1. Let's start with the easiest : Warren Frost
and Grace Zabriskie
They played Susan Ross's parents in Seinfeld
2. Brenda Strong
The braless wonder Sue Ellen Mischke in Seinfeld
3. Walter Olkewicz
The cable guy from "The Cadillac" episode
4. Ian Abercrombie
The awesome Mr Pitt in Seinfeld
5. Frances Bay
Jerry's marble rye victim Mrs Choate
6. Molly Shannon
She played Sam in the episode "The Summer of George"
7. John Apicella
and Jerry's repairman in "The Tape"
8. Jed Mills
Joel in "The non-fat yogurt"
9. Jack McGee
Ralph in "The Pothole"
10. Don Amendolia
The hansom cab driver from "The Rye"
11. Clive Rosengren
He played a waiter in the episode "The Wink"
Source : Imdb