All-girl opponents! Momma Bosco is already there, (so is Stinky, but who'd want to play poker with her?) just add Marzipan, Morgan and... uh... is there a female character in TF2? Cortana maybe? I'd definitely vote for GlaDOS. That does mean there'd be two Telltale characters and no Penny Arcade one, but Tycho's niece is too young and I can't see his wife there.
ETA: I would have suggested adding Sybil instead of Momma Bosco, but I'm still mentally scarred from her appearance in Devil's Playhouse. PENNIES?!
"Gentlemen! Please! You can fight like itsy bitsy babies later. Right now we have adult name-calling and mud-slinging to attend to."
- Dr. Nightmare, Attorney at Law