Just remember: if an ability is a passive or has a passive component (Agent Coulson), does damage to or stuns the character that uses it (Juggernaut, IM40 yellow), depends on owned tiles on the board (Patch red), or changes based on conditions (4* Punisher), it’s not eligible to be a teamup.
3* Luke Cage’s yellow, which can be given out, counts your center character as Luke Cage for purposes of determining how many allies are still standing, so it’ll only ever count up to two.
This is not true, unless it was changed recently. Nova yellow and 3* Luke Cage yellow teamups can count up to 3 allies, if your whole team is still standing. This means those 2 abilities are better when used as a TU than normally by those characters.