Has anyone noticed the show from the early 80's which was released on ABC called "Fridays"? It was ABC's competition to Saturday Night Live...If you remember the Ronald Reagan character was actually played by Michael Richards and he was funnnnnnnnnny.
Other Fridays cast members who appeared in Seinfeld were:
1. The Rabbi: Bruce Mahler
2. The man who sold Elaine the Jake Jarmel glasses: Danny Breen
3. One of George's girlfriends (in the episode where Eric the Clown put the fire out with his shoe): Melanie Chartoff
...All Fridays cast members
Then Melrose Place:
1. Dr. Sara Siddereedees (not sure of spelling): Marcia Cross
2. Jerry's girlfriend, Jenna, (toothbrush in the toliet): Kristin Davis
3. George's city guide, Mary Ann: Rena Sofer
4. Elaine's boyfriend, Tony, who takes George and Kramer rock climbing: Dan Cortese
5. Elaine's boyfriend who delivers the couch and does not agree with Elaine on the pro-choice/pro-life argument: David James Elliott
6. The father of "See the Baby" in "The Hamptons" episode. Don't remember his name...
All 6 of these people were regular members of Melrose Place
And of course, there's the episode where Jerry revealed that he liked Melrose Place. Even if that episode never aired, I still would think that he likes Melrose Place from all the melrose place characters that show up on the show.