A call for season one art requests yielded a couple for more character stuff. The truth is there isn’t that much beyond what we’ve posted already. The exception is with Yo, though (Cristina’s request, by the way).
Eric originally designed the Chum Chum-loving character less refined, larger, and a bit more oafish (above). Visually, as Chum Chum’s nemesis, she’d play off him more comically; she’d be like the show’s Lennie, hugging, petting, and squeezing Chum Chum at every opportunity. However, the idea of a character - even an incidental one like Yo - not being cute in the traditional sense didn’t wash with the network. Kicked back to Eric, Yo was re-designed into the more spastic version we know today (the bottom of this post).
Besides her early and final versions and a pair of color models, included here are a few variations and expression sheets, closer to the final Yo, by Eric himself (he draws good).
Thanks for the suggestion, Cristina.