Ab Van der Linden appeared in many different roles. In one story arc he portrayed both an ordinary doctor and an African Witch doctor. He briefly appeared dressed up as his alter ego "Flappy de clown" (uncredited) in a very early episode.
Only two characters changed their costumes during the series. 't Heertje's suit changed from black to light brown in the very first week. Tika had a more obvious costume change, explained away by having her pick out a new outfit from great great grandmama's magic dress up book.
Of all the human characters, only the farmer (played by Sies Foletta) never panicked or found the magic occurrences around him abnormal. This was because a "normality" spell was cast over him in one of the earliest episodes.
The character 't Heertje's first name is Frederik. Kwark's little heard first name is 'Constant'.