well,t hat's the thing. the end credits are just a series of stills, and i've not yet seen an episode where these characters are featured. (this only compounds my suspicions, because all the other characters in the end credits are the main repeated characters. to have a pair of singularly occurring characters in the series actually appearing there...that's suss)
the song to atomic betty is sung by a female voice (but then again, so is "don't cross the street in the middle") and is just strange enough to possibly be a tmbg-influenced piece.