Just my opinion: There ain’t no doubt that an uncredited Scatman sings the title theme
The credits are actually listed at the end of the cartoon, not in the intro, but Scatman is not listed among the voices.
Anyone else wanna opine?
I’m not sure. Here are two theme songs Scatman did that he is credited on for comparison:
(And isn’t “Scatman” an awesome name? Who wouldn’t want to be Scatman?)
When was the song recorded? Scatman John is dead. (That’s the guy you mean, right?)
NM, there are apparently two Scatmans? 
Says the Scatman John I linked is John Larkin. Hmmm… Sorry! I see, one is Scatman John, the other Scatman Crothers. ETA: But both are dead, Scatman Crothers has been dead longer than Scatman John.