Just a quick little thing I decided to do, lets get started.
1. Teenage Mutant Ninja Turtles: I can see this team up be pretty well played out, plus Donatello would be in heaven if he were to see the lab Hiro and the gang work out of, plus, Mikey and Fred would make an awesome bromance and trade comics with one another also, Baymax and Ice Cream Kitty......let that image fester in your mind.
2. Avengers: Earth's Mightiest Heroes: I think the BH6 would be in total awe of being around Avengers Mansion let alone meeting the likes of Tony Stark and Hank Pym, and if this was a same universe deal, I can see everyone of the BH6 besides Baymax totally geeking out over meeting Ironman, even having Hiro try and incorporate Stark technology in with their suits
3. The Fantastic Four: Again, if this was a same universe crossover, the entire BH6 team would geek out over meeting Reed Richards, Johnny, I an see trying to hit on Honey and Go Go, Herbie meeting Baymax would be fun to see and it would just be fun to see a group of veteran heroes show the rookies the ropes
4. Ultimate Spiderman: To the show's credit it is getting better and it has Spidey universe hopping, so who knows, maybe we can see Peter wind up in San Fransokyo and meet up with the BH6, lord knows this would be the crossover that would make the most sense and could in theory pave the way for a Big Hero 6 animated series
5. Transformers Prime: Obvious fan boy reasons are obvious.
6. Star Wars Rebels: Another one of Disney's new shows/spins on a beloved property, it would be cool to see the BH6 encounter aliens and have Hiro and the gang examine the tech in Star Wars
7. Jet Jaguar: Come on, this would just be too awesome not to see Jet Jaguar help the BH6 out with fighting a monster by using his preferred tactic of "PUNCH! PUNCH! PUNCH!"
8. Gravity Falls: This and number 9 need a little more explaining than the others but Gravity Falls has dealt with some weird crap in the show and Dipper and Mable getting sucked into the BH6 universe or the BH6 getting sucked into the Gravity Falls universe, wouldn't sound too out there for them, and having Mable meeting Baymax and introducing him to Waddles would just be adorable, plus Fred meeting Robbie and the two being like "your voice sounds familiar" props to those who got the joke.
9. Ed Edd n Eddy: God help us if Fred lets Ed get in his super suit, we all saw what big Ed did in a regular costume, now think of the damage he can do if he can breathe fire and have super strength, plus I think Double Dee and Wasabi would think of each other as soul mates giving their personalities
10. Big Hero 6 Comic: Yeah, why not have the movie version of the team meet their comic counterparts, and see how different they are from one another, especially Honey Lemon and Wasabi.
11. Randy Cunningham 9th Grade Ninja: Another Disney cartoon with a Japanese meets American culture vibe to it.
12. Teen Titans: Another obvious reasons thing