The back cover for the game has a bit of a screw-up: the description used for Rampage is actually describing Rampage 2: Universal Tour! Here's the complete description:
"Shocking! Scumlabs International has made yet another mistake by messing with nature, and now the ugly beasts of their science experiment are fighting back. This time, new mutants Curtis the Mouse, Boris the Rhino and Ruby the Lobster have to obliterate numerous cities in order to rescue the original mutants (George, Ralph and Lizzy). Of course this wouldn't really be a universal tour unless you also defended the earth from an alien attack"