I recall when he came into the program (Hazel) and essentially replaced Don DeFore (although he was a different character). The show never worked as well for me again...
Can't find much of anything on Fulmer. Fortunately there's a ton of stuff on DeFore.
At this site there is a 'family' photo of him with the Hazel cast: Hazel
I'll keep looking for more on Fulmer.