Tread Perilously sets down at Rockefeller Center for two episodes of 30 Rock: "Greenzo" and "Hiatus."

In "Greenzo," David Schwimmer appears as a focus-group and NBC/Universal approved non-judgmental conservation mascot. But as will happen, the power goes to Schwimmer's head. Meanwhile, Liz finds herself accepting another invitation to another of Kenneth's lame parties. This time, though, Tracy spreads a rumor that T.I. is going to the party. Hilarity ensues and Liz vomits on a demon.

In "Hiatus," Tracy's attempt to evade the Black Crusaders leads him to Needmore, PA. There, he stays with Kenneth's cousin Jesse, who has his own designs for Tracy. Meanwhile, Jack's mother takes an immediate dislike to his fiancee. The situation leads to Jack having a heart attack. Also: Jason Sudeikis appears.

Sitcom Correspondent Paula Dixon joins Erik and Justin as Erik once again indulges in his disdain for David Schwimmer. Justin revels in his disinterest toward The Black Eyed Peas. Paula professes her admiration for Dot-Com, she also defends all Paulas working in the industry. Erik completely forgets about Josh. Paula discovers how hard it is to say "chlorofluorocarbon." Erik proclaims that his sarcasm is sincere. And in a throwback Thursday to good and simple times, Erik and Justin tell Paula about covfefe.