Sam Marin originally auditioned for Skips, and Mark Hamill originally auditioned for Pops. Marin and Hamill switched roles after their voices didn't sound right for the characters for which they auditioned.
Unlike most Cartoon Network shows, this show was known for its use of licensed music. Many of the songs were usually 1980s music, which was the kind of music to which series creator J.G. Quintel grew up listening.
High Five Ghost is the only character to have a shadow.
Originally, the show was to be called "Normal Show," and two animals (similar to Mordecai and Rigby) would work at a zoo where the animals would be humans.
Adventure Time (2010) and this show were the first Cartoon Network shows to be renewed past six seasons.