Some of The Muppets' more popular puppet costars are conspicuously absent from this animated version, except in stock clips from The Muppet Show (1976) and related projects. Most of Doctor Teeth's Electric Mayhem Band are absent because their Muppet Show gags revolve primarily around thinly veiled indications of drug use, a big no-no for a children's show. The exception is their drummer Animal, whose shtick is simply being insane and feral, which is apparently OK for children to see. Crazy Harry, an active vandal who goes one step beyond Animal in the lunacy department, was probably seen as a bad role model whose appearance would have jinxed the show's chances of being made. Uncle Sam Eagle, the sourpuss straight-man of the Muppet Show, doesn't suit the playful, anything-goes mood of the cartoon and would have been off-putting to children. Rizzo the Rat was probably too unappealing and/or unnecessarily redundant to other characters' functions. It is odd and inexplicable that Sweetums the Monster was left out, considering the enduring popularity of his fellow Monsters on Sesame Street (1969), aimed at the same demographic - perhaps it was an issue of time and cast constraints on the series. The absence of most other characters including Swedish Chef, Lew Zealand, Beauregard the Janitor, and the Statler & Waldorf duo, can probably be chalked up to the fact that it's a bit difficult, even with the most permissive Muppet logic, to even imagine these characters as babies.