All references below are from Den of Geek, unless stated otherwise.
The cover of People Magazine’s November 17, 2010 issue (where Ryan Reynolds was named “Sexiest Man Alive.”)
The inside of one goon's wallet is seen in the opening credits, containing a picture of the goon dressed as a superhero with a bright green mask and ring, referring to Reynolds playing Hal Jordan in DC Comics' Green Lantern film.
Wade remarks that he doesn’t want his superhero suit to be green or animated. Both a reference to Ryan Reynolds’ Green Lantern stint and the fact that the Green Lantern costume was entirely animated.
Wade happens to own an action figure of Deadpool from X-Men Origins: Wolverine for the sake of jabbing at that movie’s terrible portrayal. As a joke, he wants to show Vanessa the greatest thing in the world, and picks up the toy... and the vinyl music record it's sitting on top of. He shows her the record.
Ajax suggests sewing Wade's mouth shut. While working in the context of the scene, Wade tells him that it's a bad idea, a reference to the unpopular depiction of Wade Wilson in X-Men Origins: Wolverine.
When freaking out after Vanessa's kidnapping, Wade mutters a line beginning with "Cock juggling [inaudible]..." which could be a reference to a similar line used by the character played by Ryan Reynolds in Blade: Trinity.
On the Deadpool board in Sister Margaret's someone bet on R Reynold to die.
While recovering after the freeway fight, Wade is being consoled by his blind friend, who urges him again to go after Vanessa. Wade demurs, citing his looks, and adds, "Do you think Ryan Reynolds got this far on his superior acting ability?"
When beating up Ajax, Deadpool refers to himself as being from Regina, Saskatchewan. Deadpool's nationality is something that bounces back and forth in the comics depending on the writer. Some say he's American while others say Canadian. The latest run with him has basically solidified the idea that he's Canadian.
Weasel suggests Wade should star in a horror movie and likens him to Freddy Krueger. It's a comparison that's been made several times in the comics, most recently by Kate Bishop Hawkeye, who thought it was a Halloween costume and was instead mortified to realize it was actually Deadpool.
With a knife in his skull, Deadpool sees little cartoon characters crowding around Vanessa. Ever since Daniel Way took over writing Deadpool (starting with Wolverine Origins #21), he started a regular gag where Deadpool would see the world differently like that. It's been referred to as Pool-o-Vision.
Wade gets ready for the final battle with the line, "Time to make the chimi-fuckin'-changas." During Vol 1, and Cable/Deadpool, he randomly says chimichangas and some of the fandom latched on. In Cable/Deadpool #13, Deadpool is in a restaurant that makes the best chimichangas on the island. Then he specifically says "Don't even like chimichangas all that much. I just love saying it.". He immediately orders an Enchilada instead. That line has been ignored, and somehow the fandom stuck to the idea that he loves chimichangas. This is also a reference to the famous "Time to make the donuts" commercial for Dunkin Donuts from the 1980's.
Wade’s incident with the pizza guy is heavily based on a scene from Daniel Way’s run with the character. It’s from Deadpool v.2 #10. Despite the movie’s R-rating, the comic version is a lot darker. It isn’t just a case of stalking countered by intimidation, nor is it about teenagers. The pizza boy ruined Deadpool’s client’s high school life, which carried over into her adult life, due to spreading some horrible rumors about her.
The playful, sexual way Wade messes with the pizza boy ties into Deadpool’s pansexual nature, which director Tim Miller insisted they play up. There are loads (heh) of other references to Wade's fluid sexuality in the movie, too. Arguably, many people believe, based on different interpretations of the character's history, that it's just a way Wade talks and acts to mess with people's heads while working/fighting.
During one scene, Wade is wearing a shirt with Bea Arthur on it. In a running gag that started in Cable/Deadpool #1, Deadpool considered Bea Arthur to be the sexiest woman in show business.
The pizza is from Feige's Famous Pizza. Kevin Feige is the president of Marvel Studios. (Thanks, Jim the Nickel and bittergourd!)
Vanessa Carlysle, otherwise known as Copycat, is Deadpool’s original flame in the comics. Technically, she appeared first in New Mutants #98 along with Deadpool, in the sense that in the comics she’s a shape-shifter and was really pretending to be other new character Domino. They didn't reveal that fact until several issues later. Prior to that life, much like in the movie, she was a prostitute.
After Vanessa makes a reference to Empire Strikes Back involving Yoda, Wade remarks that it's like he made her in a computer. Likely an allusion to the movie (and later TV show) 'Weird Science' about a couple nerds who made the perfect woman using their computer.
The idea of Wade wanting to leave Vanessa behind out of fear of her seeing him die of cancer is lifted straight from the comics. It was briefly shown in the first Deadpool miniseries, Deadpool: The Circle Chase (1993), and was revisited in Deadpool v.1 #-1.
Wade jokes about "boomboxing" the WHAM! song "Careless Whisper," which is a nod to 'Say Anything'..., the 1989 movie where John Cusack holds his stereo over his head, playing "In Your Eyes" by Peter Gabriel in order to serenade his girlfriend.
As reader Francisco Lourenço Ribeiro points out, the scene of Vanessa going into the rainy alley to get kidnapped by Ajax may be based on the scene in Spider-Man where Mary Jane is saved from muggers and Peter hides in the shadows. This is supported by Weasel telling Deadpool, "Go get her, tiger," what with "tiger" being Mary Jane's trademark thing.
Weasel has been Deadpool’s go-to weapons and tech guy since the first Deadpool miniseries, The Circle Chase. He was created by Fabian Nicieza and Joe Madureira. Real name Jack Hammer (yes, really), Weasel is actually improved by the movie’s take. Mainly because in the comics, Weasel is the one constantly taking abuse from Wade, which just makes Wade look like a bully. (Side note, Wade was a bully, an actual villain, at the start. His relationship with Weasel improves greatly as Deadpool becomes an anti-hero and then on his current heroic attempts).
Sister Margaret’s School for Wayward Children, otherwise known as the Hellhouse, is another Joe Kelly creation, appearing in Deadpool v.1 #1. Run by an old man named Patch, the Chicago-based clubhouse was a place for mercenaries to hang out and get job offers. This was mainly used as an excuse to have Deadpool constantly butt heads with his main (at the time) arch-nemesis T-Ray.
Liefeld is one of the names on the Dead Pool (see? Told ya there were more references to Deadpool's creators). Wade even acknowledges one of the mercs by that name.
When Wade orders the blowjob drink at the bar, the waitress' name is Kelly. Joe Kelly wrote Deadpool in the late-90s and is credited as being the writer who truly gave him life as a three-dimensional character.
The Dead Pool board has a lot of Easter egg names mixed in there. Hell if I have the full list, but I did see "M. Tyson" and "S. LaBeouf" mixed in there. Give it some time. I'm sure someone will have a screenshot. A few other names noticed are C. Sheen, K West, W Wilson, V Putin, R Reynolds, TJ Miller,B Cosby, O Osbourne, J Nelson, L Lohan, and M Cyrus.
The Dead Pool is a thing from the comics, but not at the Hellhouse. It was originally at the Hospice, where rejects and failures from the Weapon X program were sent to die (peacefully, but it turns out worse).
Colossus, real name Piotr Rasputin, is the oldest Marvel character in this movie, debuting in Giant-Size X-Men #1 in 1975. He was created by Len Wein and Dave Cockrum. Despite his big inclusion in this movie, he has very little history with Deadpool in the comics. They fought briefly during the Daniel Way run of Deadpool and in a time-travel story, the two were in a future incarnation of the X-Men. He's just as much a boy scout in the comics as he is in the movie. The movie really plays up the Papa Bear aspect.
Deadpool compares Professor Xavier to Heaven's Gate, a religious cult that existed for a few decades and made news in 1997 when its members killed themselves, believing that their souls would be picked up by UFOs and brought to Heaven.
Deadpool destroying his own limbs in an attempt to fight Colossus and failing every step of the way is a bit of a reference to the Black Knight from Monty Python and the Holy Grail. In the original leaked script, Deadpool even calls it out more blatantly. He even references Colossus as RoboCop ("Dead or alive, you're coming with me!"), which goes well with the agonizing, Verhoeven-esque, over-the-top violence of the scene.
Colossus talks about bringing Deadpool to the Professor, and he asks if it's going to be James McAvoy or Patrick Stewart, as the new timeline thing is really confusing. Obviously he's breaking the fourth wall and talking about the events of X-Men: Days of Future Past and how it affects the X-Men movies' continuity.
Deadpool warns about spoilers for 127 Hours, which ended with James Franco cutting off his own limb to escape.
When Deadpool's blood splatters all over Colossus' face, he jokes, "Are you there, God? It's me, Margaret." A reference to the book of the same name by Judy Bloom, which is about a girl having her first period.
The way Deadpool falls off the bridge and lands in a garbage truck as it drives off is very much like what happens to John Cusack in the movie Better Off Dead, though his fall was far more accidental. (Thanks to Oeno)
Deadpool owns an Adventure Time watch. The joke is basically the reference, I guess. You're on the internet. You already know what Adventure Time is. You have to. The joke also being that a fully grown man like Wade watches a children's cartoon.
Wade also likes Voltron, Hello Kitty, and other childish franchises.
When joking about fondling Wolverine's balls, he starts speaking in an Australian accent and mentions "down under," a more direct reference to Hugh Jackman's nationality.
One of the prominent signs on the freeway says "Parker Boulevard." As reader Mike Priest points out, this could very well be a reference to Spider-Man. My first reaction was that it might be a reference to comic writer Jeff Parker, but that guy's written like a single Deadpool comic in his career, so that's not too likely.
Deadpool constantly refers to the recruiter character as Agent Smith, likening him to the cold, suit-wearing villain from the Matrix movies.
Later in the movie, Deadpool attacks the recruiter while calling him Jared and makes a joke about a footlong. This would be innocent on its own, but considering Wade made jokes earlier about the recruiter seeming like a child molester, this is most definitely a topical joke about Jared Fogle's recent arrest and conviction for being a pedo.
Joking about Batman and Robin’s sexuality is old hat, but most famous for Fredric Wertham’s attempts to bring down the comics industry with his book Seduction of the Innocent.
When Ajax and Angel Dust leave Sister Margaret’s, Weasel makes fun of them for dressing like they’re going to go watch Blade 2. Blade Trinity starred Ryan Reynolds as Hannibal King, another Marvel [Deadpan Snarker] 12 character which inspired many to think he’d play the perfect Deadpool. Frankly most of Reynold's characters are Deadpan Snarkers.
The way Deadpool impales the final goon with two katanas and holds him up is very reminiscent of the Adam Kubert cover of Wolverine #88, the first ever meeting between Wolverine and Deadpool.
Stan Lee has his expected Marvel cameo, this time as a strip club DJ. What’s funny and notable about this is that Stan Lee didn’t co-create a single character in this movie. Explicitly called out as a Glorified Cameo during the title sequence, similarly to many other roles in a tongue-in-cheek manner.
Stan Lee did create 'Stripperella', a mature (non-porn) adult cartoon super-heroine, who is a Stripper, making the cameo less random than it seemed.
Voltron: Defender of the Universe was a cartoon from Japan in the mid-1980s where five pilots would control giant lion mechs, then combine them into a sword-swinging robot.
Wade talks about his Liam Neeson nightmare, where he goes into a tangent about the Taken trilogy without outright identifying the movies by name. The choice of Liam Neeson as the butt of the joke might be due to Neeson's role in Darkman, another movie about a super-antihero with disfigured face. (Darkman was directed by Sam Raimi, who also directed the 2002–2007 Spider-Man trilogy.)
During the bit where Deadpool's freaking out over hitting a woman, he throws off an attacker while yelling, "Get off me, spider monkey!" As pointed out by reader Jason Aniceto, this is taken from the first Twilight, where Edward tells Bella, "You'd better hang on tight, spider monkey," while she was on his back in similar fashion.
It's more likely a reference to Deadpool Vol 2 #19-21, 'WHATEVER A SPIDER CAN'. Deadpool and Spiderman team up to stop Hit Monkey. Yes, Marvel has a character that's a non-talking monkey that's a hitman. You don't believe me.
When going after Ajax, Deadpool brings with him a copy of the November 25, 2008 People Magazine where Hugh Jackman was awarded "Sexiest Man."
One of the experiments in the facility where Wade gets his powers has bones sticking out of their back. This is likely a reference to X-Men character Marrow, who constantly has them jabbing out of her back and can regenerate them at will. Marrow is also in the video game series Marvel vs. Capcom, where Deadpool was added as a fighting character in MvC 3. Alternatively, it can be a reference to Spyke, a mutant that was introduced in the cartoon X-Men Evolution, and is Storm's nephew. He also has bone spikes like Marrow.
The final battle between Deadpool and Ajax takes place on a dismantled SHIELD helicarrier. The original concept art makes this pretty blatantly obvious, but the artist was asked to downplay the resemblance (presumably for legal reasons).
Before the end credits, he calls himself "your friendly neighborhood pool guy", yet another jab at how similar he is to Spider-Man (whose trademark catchphrase refers to himself as "your friendly neighborhood Spider-Man"). They are constantly confused for each other in-universe in the comics.
Deadpool calls out the lack of inhabitants at the X-Mansion other than Negasonic Teenage Warhead and Colossus, questioning whether the studio could not afford any other X-Men. [thanks to @nickson104]
During the animated end credits, Deadpool dangles in the upper right corner of the frame while upside down and apparently from a web string, much like Spider-Man is seen to do.
When Negasonic Teenage Warhead is finishing her Tweet before attacking Angel Dust, the fuselage of a wrecked aircraft is in the background. The registration is C-FLNT, a likely nod to Captain Flint of the Howling Commandos.
One scene has a closeup of Wade's headboard covered in stickers. Some of them resemble the TOPPS 90's X-Men stickers, one of which looked like Apocalypse, the villain for the upcoming X-Men movie.
During the final battle he has stapled a photo of Hugh Jackman on his face, just in case he loses his mask.
There are also at least 3 Monty Pythonesque references. The competition between Wade and Vanessa over who had the shittiest upbringing is a nod to the "Four Yorkshiremen" skit, the "Fight" between Deadpool and Collosus is overtly similar to the Black knight scene in "Monty Python and Holy Grail", and when trying to guess Ajax's name, Wades last guess is Basil Fawlty (from Fawlty Towers) which while not from Monty Python, stars John Cleese, arguably Monty Python's most famous member.
When demanding that Ajax fix the damage done to him, Deadpool refers to his disfigurement as a "butter face". This refers to an old sexist joke:
One guy turns to another and says, "Look at that hottie!".
The other replies, "She's a butterface."
"What?"
"Y'know, a butterface. Her body's great, but her face!"
Name. Age
Cosby.B (Bill). 78
Sheen.C (Charlie). 50
West.K (Kanye). 38
Wilson.W (Wade). 39
Putin.V (Vladimir). 62
Boothe.J (Boothe was the guy Wade bet on to die. He had the waitress send the blowjob shot to another merc and said "tell him it's from Boothe." [No first name listed in credits]). 21
Reynolds.R. (Ryan). 38
Miller.TJ.(ie Weasel). 35
Lohan.L. (Lindsay). 29
Cyrus.M (Miley). 23
Rock.K (Kid). 45
Tyson.M (Mike). 49
Nelson.J. (Judd). 56
Wayne.L. (Lil). 33
Beaty.N (Ned). 78
Liefeld.R (Rob). 48
Osbourne.O (Ozzy). 67
Bynes.A (Amanda). 29
Palmer.A (Arnold). 86
Note the age on the board corresponds to the person's actual age at the time of release of the film, with the exceptions of Wade, who is a year older than Ryan Reynolds (perhaps a nod to the fact Deadpool looks older than he is), Vladmir Putin, who we can assume had a birthday between filming of the scene and the release, and TJ Miller, who is posted as 35, although IMDB and Wikipedia have him as being 34 (no idea why there's a discrepancy here, though).