Something odd I found, and figured some of the people here may be interested in. If you have Gogo mimic a 7-7-bar joker doom you used to kill the first tier of the final battle, going into the second tier, you don't get the normal "blank" joker doom. Instead, he casts another doom, but it only hits three of the four parts of tier 2, leaving the tiger guy alive. Then, you can mimic it again to get the 0 target cast, and a third time to actually kill the last part of the tier.
Seems a bit weird, my guess is that for some reason the game just slides 3/4's of tier 2 into the positions of the first tier, so when the game checks to see if they're dead as you mimic the joker-doom, it finds new, doom-able targets. (If I understand MasterZED's slot faq correctly, and I am just making this up.) Has anyone here ever seen this? I tried it a few times, and it consistently happens, but other people confirming it isn't some anomaly on my emulator would make me feel a bit less confused as to what's happening, at least.
A quick edit: If you kill a part of the first tier (break the lower arm), then joker-doom, you don't get all 3 parts doomed on the second tier when you mimic, so I think my theory above is right.