When Tom 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.
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.