In the Marvel Universe, can someone be on multiple superhero teams? For example, be part of two different Avenger teams, or be part of The Future Foundation and still be on another team?
Yes, as of June, 2010, Wolverine was splitting his time across multiple teams, including the X-Men, two Avengers teams, and although unmentioned in the panel below, The Uncanny X-Force. All this, on top of his own solo books, and various guest spots.
Also worth mentioning, is the fact that Uncanny X-Force (or just X-Force in the actual books), is a secret sub-group of X-Men. If you wish to not count that as a "separate team" and view it more as a strike squad, there is also The Avengers Unity Squad, which is specifically made up of various X-Men and Avengers members originally including Captain America, Havok, Rogue, the Scarlet Witch, Thor and Wolverine.
Even Wolverine has lost track of how many teams he is a member of.
Yes, they can.
For example, Spider-Man, who is currently on three superhero teams.
Transcription of relevant text:
- formerly the Secret Defenders
- "New Fantastic Four"
- The Outlaws