Mark Hamill was picked for the role of the Trickster, because he previously played the Trickster, In the original Flash 1990 CBS Live Action Series. He also voiced the role of the Trickster, in Justice League and Justice League Unlimited cartoons (Along side Wally West, the better Flash). He has also had an extensive career as the voice of the Joker, another DC character.
Fun fact, Henry Allen, Barry's father, played by John Wesley Shipp, who was the original Flash, along side Mark Hamill's Trickster. Funner fact, Barry Allen's full name is Bartholomew Henry "Barry" Allen, making Henry Allen also the real name for the Flash. Flash-ception.
They also rebuilt his hidden lair:
The current CW show is obviously not a direct continuation of the original, lets just assume that's Earth 3 or some other comic-y explanation.
Undoubtedly, the "I am your father" line is an intentional lamp shade by Hamill and/or the writers. Hamill is very very into his roles, and self-deprecation jokes are cool with him.
Hamill got to deliver an iconic Star Wars line when he revealed he is the father to the younger Trickster.
"In rehearsal I said 'I am your daddy,' which got a big laugh at the table read," Hamill said. "I'm sorry I didn't give them the option in filming, because I think it would have been funny to self-parody the line. But it got a big laugh. If you're happy, I'm happy."
The Trickster episode had him channeling the Joker ala Talking down to Terry "batman Beyond" McGuiness when in the cell as well:
Joker tells Luke that HE is his Father. How By His Bootstraps of him:
Luke Parody in Silent Jay & Bob Strike Back: