Lester the Lab Rat was a hand puppet lab rat for the pilot. He had a hand-controlled
mouth and full cable articulation on the eyes. The puppet performed in the pilot
that sold the show. Unfortunately, right before production time, the puppeteer
hired to play Lester became very ill (he has since recovered, thank you). Instead
of replacing the puppeteer, producers replaced the puppet. An actor in a rat
suit took Lester's place.