1 of 15 Nicole Rivelli/NBC
Jennifer Aniston as Claire
Rachel who? Aniston played an erratic friend of Liz's from Chicago who couldn't keep her paws off of Jack. We particularly loved how she referred to their romps as "riding the F train."
2 of 15 Nicole Rivelli/NBC
Oprah Winfrey as Herself/Pam
After self-medicating with Comanaprosil, Liz hallucinated that the "spunky tween" sitting next to her was actually the talk-show queen
3 of 15 Nicole Rivelli/NBC
Megan Mullally as Bev Mullally played a buttoned-up adoption counselor whose visit to Liz's office ended disastrously
4 of 15 NBC Universal
Will Arnett as Devon Banks
Jack's sexually confused adversary for the top job at NBC — and in "talking-like-this" contests — wore a short-short robe when he seduced Kenneth. That's all you really need to know.
5 of 15 Nicole Rivelli/NBC
Edie Falco as Celeste "C.C." Cunningham
Jack's liberal congresswoman girlfriend missed a crucial vote on whale torture to frolic in a central Pennsylvania mining town.
6 of 15 Anne Joyce/NBC
Carrie Fisher as Rosemary
Liz's comic idol — and metaphor for Future Liz — turned out to be a little nuts. As the erstwhile Princess Leia put it: "Help me, Liz Lemon. You're my only hope!"
7 of 15 Kent Eanes/NBC
Al Gore as Himself
The former veep was game to spoof his environmental advocacy on Rock's "Girlie Show".
8 of 15 Nicole Rivelli/NBC
Buck Henry as Dick Lemon
As Liz's dad, comic legend Henry (center) spoke the oft-repeated — and misunderstood — line: "You can't have a Lemon party without old Dick."
9 of 15 Virginia Sherwood/NBC
Chris Parnell as Dr. Leo Spaceman
The SNL vet recurs as a quack who recommends that Jenna try crystal meth to lose weight and that Tracy try to enjoy the various drug interactions of his prescriptions.
10 of 15 Kent Eanes/NBC
David Schwimmer as Greenzo
As Al Gore's environmental mascot, David Schwimmer went from cheery actor to drunken lout in the space of 22 minutes.
11 of 15 Chris Haston/NBC
Jerry Seinfeld as Himself
The sitcom legend wisely allowed the 30 Rock stars to mock him relentlessly. Not that there's anything wrong with that.
12 of 15 Nicole Rivelli/NBC
Elaine Stritch as Colleen Donaghy
Jack's Mommie Dearest made emotional terrorism an art form.
13 of 15 Virginia Sherwood/NBC
Jason Sudeikis as Floyd
Just as Liz found love with normal guy Floyd, he promptly moved to Cleveland.
14 of 15 Nicole Rivelli/NBC
Rip Torn as Don Geiss
Come on, it's Rip Torn! Plus, we loved watching Jack trip all over himself while trying to earn the job of the lame-duck NBC president on his way out.
15 of 15 Nicole Rivelli/NBC
Dean Winters as Dennis Duffy
Everyone's favorite beeper salesman reunites briefly with Liz — that is, until he appears on To Catch a Predator ("She said she was 16, but I knew she was 22.").