Giga Pets Plus
Giga Pets Plus was the second wave of Giga Pets released in 1998, and both featured multiple pets in one device, as well as voice (or sound, really) recognition.
Bugs Bunny, Taz, Daffy Duck, and Tweety are the four characters you start with, and Yosemite Sam and Roadrunner can be unlocked as you play. None of them can die, but they will leave if the score drops too low.
Take care of Tommy, Chuckie, Spike, or Angela. The instructions are written from Tommy's perspective as well, a very cute touch! They work similar to the pets, where they'll leave after 14 days unless your care is very good.