Here are some people who have worked on more than one sitcom together...

Bea Arthur & Rue McClanahan
Maude & Golden Girls

Rue McClanahan & Betty White
Mama's Family & Golden Girls

Bill Cosby & Phylicia Rashad
The Cosby Show & Cosby

Telma Hopkins & Rosetta LeNoire
Gimme A Break & Family Matters

Clifton Davis & Jester Hairston
That's My Mama & Amen

Richard Mulligan & Dinah Manoff
Soap & Empty Nest

What are some others?

Lucille Ball and Vivian Vance
I Love Lucy and The Lucy Show

Dixie Carter and Delta Burke
Filthy Rich & Designing Women

Lucille Ball and Gale Gordon
Lucy Show & Here's Lucy & Life with Lucy

Betty White and Georgia Engel
Mary Tyler Moore Show & Betty White Show

Al Lewis and Fred Gwynne
Car 54, Where Are You? & The Munsters

I can think of soem

Ron Howard and Jack Dodson
Andy Griffith Show and Happy Days ( Dodson only guested a few times as Ralph's dad, does this count?)

Some of those too
THats all I can think of now lol

How about Laverne DeFazio, Shirley Feeney, Richie Cunningham, and Potsie Weber (4) on both Happy Days and Laverne & Shirley? Granted, Laverne and Shirley made a few appearances on HD, while Richie and Potsie made a few on L&S. Remember the crossover episodes, where L&S visit the farm in rural Wisconsin?

Didn't the Fonz make an L&S appearance, too? And Al Molinaro guest-starred as a priest if I'm not mistaken. Ditto with Pat Morita, the original Arnold's owner.