I wouldn’t call Schwartz a major celebrity either, in fact, I never heard of him before he voiced 3 blue cartoon characters.
Speaking of Sonic, his original voice Jaleel White used to be a huge celebrity, but only mostly for his Steve Urkel character on ABC’s “Family Matters” sitcom. Ironically, his character was a very minor bit/joke character in Season 1, but became so popular, he became a regular quickly. Nowadays hardly anyone remembers that show unless they were children of the ‘90s, and Jaleel White rarely does acting gigs, as he’s more of a sports writer now. (Though, he did guest star as the genie in the new Ducktales.)