Play as Anita : Press MP, LP, Left, LK, MK at the character selection screen.
Play as Dr. Doom : Press MK, LP, Down, LK, MP at the character selection screen.
Play as Thanos : Press LK, HK, MP(x2), Up at the character selection screen.
Double Power : Select a fighter at the character selection screen, then press Player One Start + Player Two Start.
Continue Fighting : Press Start immediately after winning a round to continue hitting the defeated character.
Disable Gems : To disable Gems in two player mode both players must press and hold Start after choosing their character until the round starts.
Change Character Color : At the character select screen move to the desired character then hold Up (if on top row) or Down (if on bottom row). After 3 seconds press any punch or kick button to select character.
Here are the different gem effects (which acts during a short time) and when you can get them :
Time gem (Red) : You are much more faster than usual.
Space gem (Purple) : Your character get unstoppable with this super armor power.
Soul gem (Green) : Your fighter slowly recovers life.
Power gem (Pink) : Your attacks are more powerful.
Reality gem (Orange, on the fifth opponent) : Your attacks have additional effects which makes them more powerful.
Mind gem (Blue, owned by Thanos) : The character can recover about 2 energy levels in a few seconds.
The gems are owned by different opponents: we have one at the beginning, then the first opponent have the following one then the second, then the third and finally the fifth (the last one is on Thanos). Characters have some special effects using some gems (for instance Magneto got an energy field around him with the Space gem, Spiderman divides himself in two similar being for symmetrical attacks using the Power gem).
Notice that we can only use the first gem in our gem stack. If you press the Start button during the fight, you will change the gem order in your stack, allowing for you to use any desired gem at any time.
When we reach the final fight against Thanos, he steal all the gems and collects them in his gauntlet. He uses them his way (for instance : space gem creates a warp which attracts and throws rocks on his enemy).