Different universes, and even universal clusters. The TF multiverse is a bit clusterfucky, since although Hasbro and Takara agree on the general structure of it, the details are a bit quicksandy, but G1 and Animated are definitely located in widely spaced areas of it.
Anyway…the Animated folks originally wanted Eric Idle to reprise Wreck-Gar, but he wasn’t available for some reason, so they decided that since Al did the Junkions’ theme song, they’d see if they could get him…and they could.