Some comedian/actors are given creative freedom and improvise at times when producing a new film. Is there any evidence that Vince Vaughn or Owen Wilson improvised in any scenes, diverging from the script, in the film Wedding Crashers?
@LaurentPireyn highlights a good example of their improvisation in the "lock it up!" banter over on IMDb, but there is more out there.
There are a number of sources in which Vince Vaughn and Owen Wilson speak to their methods of improvisation and their freedom to do so. One mentions how they "rehearsed improvisational lines over games of backgammon or ping-pong." Another includes co-star Isla Fisher in the improvisational mix. Still another provides this quote providing more detail about how they prepared (or didn't prepare) for deviating from the script in scenes:
Additionally, Isla Fisher mentions that Vince Vaughn encouraged her to improvise and was very supportive of her efforts when sharing a scene together here.
An expansive document including a film synopsis, actor bios and interviews with members of the production team at Hollywood Jesus (a .pdf-- questionable source, but interesting info contained within) speaks further to the improvisational environment during filming. According to Owen Wilson,
Producer Andrew Panay:
Director of photography Julio Macat adds a note from his perspective:
Director David Dobkin is "...a strong believer in script develeopment," continuing "Owen and Vince always make significant and substantial contributions to story and character."
Finally, after comparing a handful of quotes mentioned in the IMDb 'Memorable Quotes' page for the movie to the script located here, many popular lines are not present in the script (though naturally, there are a few exceptions).
I concede that discrepancies between this script and the actual film do not necessarily indicate heavy improvisation, but they may -- and that possibility is worth considering in this case, given the quotes above.
So to answer your questions @SethRogers: yes, they improvised and yes they deviated from the script-- heavily at times.
According to the trivia on IMDb, Owen Wilson and Vince Vaughn improvised the "Lock it up!" banter. As I understand it, that also means the other scenes did not - or only slightly - diverge from the script.