As far as I know in the realm of TV, only two characters that were based in a comedy series had moved into a drama series: Lou Grant from The Mary Tyler Moore Show to the drama Lou Grant, and while the movie and first show was a more comedy/drama mix...Trapper John from M*A*S*H to Trapper John, MD.

What other characters from shows with a primarily comedic bend could have lent themselves well to a drama show?

Technically, for legal reasons Trapper John MD was a spin-off of the movie MASH and not the series M*A*S*H,

There was a thread earlier about what constitutes a spin-off, but I'd think you'd want it to be the same actor, too. Trapper John MD wasn't even the same actor.

I think there's an argument that Mike Stivic from AITF might have worked, as a sort of Lucas Tanner teacher in California, dealing with serious issues affecting kids in the 70s and 80s. Many AITF episodes centered around serious topics, and Mike was passionate about them.

Robert Young went from Father Knows Best to Window on Main Street (comedy/drama), but primarily to Marcus Welby, M.D. (for which he won an leading-actor Emmy).

yea, I also think Rob Riener would have been good as a teacher in a comedy-drama.