HELP!! Marvel Vs Capcom 2 ARCADE?

What you're asking about is call the Hyper Cancel. What you need is 2 or 3 full energy bars and then you perform a hyper combo with the character you have out. During the combo, before it ends, you push the input for the next character's hyper combo in your lineup, and they jump in and continue with their own move.

Example: Iron Man, Ryu, Morrigan

If Iron Man is the character you're playing, and you have 3 full bars, push down to forward, and 2 punch buttons, and he will activate Proton Cannon.

Before Proton Cannon is finished firing, push down to forward and 2 punch buttons AGAIN, and Ryu will step out and continue the combo with his Shuryuu HadoKen.

Before that is over, then you push down to forward and 2 punches again, and Morrigan will come out and fire her Soul Eraser, continuing the combo even longer.

Basically, it's the next person in your lineup interrupting the person before them, and if the first person connects, then the second will continue, and it's a really safe way to swap your characters out. But some combos don't link up very well, so you gotta test em out.

If I remember correctly to do the 3 person combo you have to have at least 3 super bars obviously and then it's two full clockwise circles and then either both punches or both kicks. Usually both punches or both kicks would distinguish which 2 person combo you would do but with 3 person combos it doesn't matter.

OH DUDE!

You are awesome. I freaking LOVE that game. In point of fact, my girlfriend bought it for me as a christmas present for my PS2 and it cost freaking $100. In any case, I don't know the ARCADE controls, but I've always just button mashed the hell out of the thing and it's seemed to work out just fine mostly. All sorts of crazy combos and supermoves poppin' out.

Give it a shot, it's really fun.

-Knux