Here's the official NBC episode description:
"When their Kabletown bosses announce they will no longer pay for 'TGS' to be a live show, Liz Lemon (Tina Fey) and Jack Donaghy (Alec Baldwin) realize their lives will actually be easier if they shoot canned episodes fast and cheap. Only Kenneth the Page (Jack McBrayer) objects, urging that nothing can replace the communal experience of live television. He tries to convince the 'TGS' staff to fight for their right to be live by taking them and our audience through a magical look back at the illustrious history of Studio 6H."
A look back at the history of the studio will probably provide plenty of opportunities for special guests. The first live episode featured guest appearances by Jon Hamm, Bill Hader, Rachel Dratch, Cheyenne Jackson, Julia Louis-Dreyfus and Matt Damon. Louis-Dreyfus, who can next be seen in HBO's "Veep," played Liz Lemon for a few scenes in place of Fey.
"Using Julia Louis-Dreyfus to play Liz Lemon in flashback scenes was the most genius idea in the world," "30 Rock" director Beth McCarthy-Miller told The Hollywood Reporter. "She was so perfect."
Like Season 5's live episode, appropriately titled "Live Show," the cast will perform two shows, one for the East Coast and one for the West Coast. The first live episode delivered big ratings for "30 Rock," a department the show has been hurting in in its sixth season. "Live Show" had a 3.1 rating in the 18-49 demographic and a total of 6.7 million viewers, making it one of "30 Rock's" highest rated episodes.