During the opening credits we see a gallery of Freakazoid's villains. Among them is a skeletal figure in Western garb; this character does not appear in any episode of the series.
During the end credits of each episode, the character of Emmitt Nervend is given a different joke credit (e.g. Dan Riba's barber, Santa's helper, etc.). In addition, the credits for first season episodes hint at how many times you can find the character in the day's episode.
After the end credits, Freakazoid appears for about 2 seconds. In every episode, he says something different.