Liz's early acting role
A contender for the finest episode the show ever did was season three's "Apollo Apollo," which sees Liz trying to convince Tracy that he's going into space, while Jack tries to regain the pure happiness that made him throw up at a childhood party. The episode culminates when Jenna, taking revenge on Liz, shows the staff an early acting appearance by the show's head writer. Saying any more would be ruining the fun.
Liz's talk show
One of the series' finest episodes comes in the otherwise patchy season four, in "Dealbreakers Talk Show," where Liz gets a pilot based on a TGS talk show skit. The filming of the opening credits (seen below) not only showcases Tina Fey's always-excellent physical comedy skills (we tried desperately to find video of her eating a footlong subway sandwich in an airport, but no dice), but also an inventive gag involving an HD camera that keeps on giving.
My Single Is Dropping
While it's not as experimental as "Community" or "Louie," "30 Rock" could be formally playful, with bottle episodes, live shows, movie tributes and more. One of the more successful experiments were the two "Queen Of Jordan" episodes, parodies of Bravo's 'Real Housewives'-type reality shows that came about due to Tracy Morgan's indisposition due to a kidney transplant. Focusing on Tracy Jordan's wife, the two episodes are full of highlights, but none funnier (or briefer), than Mrs. Jordan's mention of her upcoming record release.
Alfie & Abner
Speaking of formal experimentation, the show's fifth and sixth seasons saw two star-studded live episodes, using the SNL studio and crew. The first was an uneven, slightly awkward attempt, but the second was a triumph, one of the best episodes they ever did, thanks to a sketch-show-type format that paid tribute to the tradition of live TV. The best moment came with "Alfie & Abner," an "Amos & Andy" parody featuring Tracy Morgan and, in blackface, regular show scene-stealer Jon Hamm. It's a classic "30 Rock" example of having their cake and eating it; letting Hamm go broad and borderline offensive with his performance, but having the joke be on him, rather than on Morgan. And being live, you can see several cast members, including Baldwin, break up from laughing too hard.
It's hard to think of a sitcom -- or TV show in general -- which can claim that its last season might be its finest, but "30 Rock" has made a damn good case for that over the last few months, with season 7 being incredibly consistent, hilarious, and even touching. And perhaps the finest new addition is "Hononym," the fake game show that's appeared several times across the season, part of Jack Donaghy's plan to deliberately tank the network.