I've recently started rewatching season 1 and one thing I'm starting to notice is that this show has actually gotten even funnier as time has gone on, which is very rare in comedies. They tend to reuse a lot of the same "gags", but even a "lesser" episode like Ep3 from season 3 is on-par with some of season 1's best episodes.
Also, Colin wasn't really that funny in S01, whereas he's a fucking riot in S03 and started really picking up steam in S02. To me, Nandor was mostly the star of S01 and has gotten less funny over the seasons, whereas the other 3 have gotten funnier.