Late in Eric's run of episodes, a start at a plot arc was developed, with Eric discovering the transition is caused by adrenaline, and meeting up with an adult (Played by Anthony Head) who has the same affliction.
When Thomas Aldwinckle (Eric's friend Roy Ackerman) left the series, he was replaced by Sarah Smart as Eric's tomboy friend Rachel Hobbs. But, filming was interrupted for a while when Smart broke her leg.
The 1st season had an animated opening titles/closing credits. All opening titles/closing credits onwards was live action.
Eric and Rachel made a cameo in A Dog Called Rex (#6.1). They are seen walking passed Rex. Eric and Rachel are discussing on why Eric lost his ability to change into a dog and they contemplate on if it another person could also change into a dog. The scene was written, in order to make the transition from Eric to Rex. Hence, passing the torch onto the new character.