This is a revision of "The Simpsons: Bart vs. The Space Mutants." The "Rev A" designation suggests a later version of the game, which could contain bug fixes, minor gameplay adjustments, or other small changes compared to the original release.  Without more specifics about the changes introduced in revision A, the core gameplay remains similar to the original release.

Simpsons, The - Bart Vs The Space Mutants (USA, Europe) (Rev A)

Silver in Sonic 2