By autofiring B while holding a red shell with Yoshi, the sprites are overloaded and this tends to either crash or just lag the game. Sometimes, more interesting memory corruption can occur, as shown in this TAS. Cause is probably VRAM overload, since I found that two sprites of ID FF also tends to crash the game. Could lead to ACE? Not the discoverer of the glitch.
I don't think the ROM I have is very good.