Earthshock, Arc of Infinity and Snakedance (Fifth Doctor).
Three excellent serials. Adric was too much the whiner in Earthshock but the writer made good use of his character and gave him an interesting death.
I was glad to see Omega again in Arc of Infinity but Stephen Thorne's performance in The Three Doctors was better that Ian Collier's.
The Mara are an interesting villian that I wouldn't mind seeing again on modern Who. That said, while they get some good development in Snakedance, Kinda was a better story.
Three excellent serials. Adric was too much the whiner in Earthshock but the writer made good use of his character and gave him an interesting death.
I was glad to see Omega again in Arc of Infinity but Stephen Thorne's performance in The Three Doctors was better that Ian Collier's.
The Mara are an interesting villian that I wouldn't mind seeing again on modern Who. That said, while they get some good development in Snakedance, Kinda was a better story.

. I may not watch every single serial (I think the fourth Doctor was around for 7 years, which would mean a lot of serials just for him) but I get how the older Dr. who format works (and the newer stuff, although it seems a lot less serialized from an episode perspective, with more one off episodes that just happen to be about double the length of the old stuff). I haven't looked too far ahead, but all the upcoming fourth doctor stuff looks great, and I'll probably work my way through his stuff for awhile.