I'm looking for a show that was on during the early years of Nickelodeon. It was live action and as far as I can remember it had maybe Jonathan Harris (Old English-like actor) playing a frail wizard. There were some gifted children that would leap from adventure to adventure.
The show had a sort of Doctor Who for kids feeling. I only caught the show in spots but remember being very addicted to it. I also remember it changing about halfway thru into a what felt like a different but related show.
I only have some vague memories beyond this that really haven't helped on Google like mazes and giant rocks. Looking up Harris on IMDB I can not find anything that resembles this and thus believe I may be wrong on the actor.
I loved this show as a kid and am more than certain that I will never track it down but any more information on it would be greatly appreciated.