As much as I liked Leo. I kinda wished they didn't put him into every episode. After all he and Billie were the only characters who ended up being in every episode of seasons. Other regulars missed an episode or two or more.
That 70's Episode is the only episode to feature just main three and nobody else, yes Mortality bites was the only one to have it in the credits, but Leo was there.
Would of been nice every season to have an episode or two that havs just the charmed ones and no other regulars in it, like Supernatural or X-Files giving the viewers a chance to explore the main stars a bit more.
I didn't see a need to have Leo in every episode of a season, I never understood why they had to have him in every episode, regardless he's married to Piper or not.