LOS ANGELES, Oct. 24  Sometimes the jokes come so fast on “30 Rock” that it takes a TiVo  and repeated use of the rewind button  to get them all.

For much of the last two weeks, on television-related Web sites, blogs and message boards, fans of “30 Rock,” the critically acclaimed but ratings-challenged NBC comedy, have been replaying and kvelling over “Werewolf Bar Mitzvah.” That six-second sketch imagines a 1980s novelty song and music video recorded by Tracy Jordan, the resident nut job on the show within a show on “30 Rock.”

As is frequently the case, explaining a joke robs it of its hilarity, so the curious are perhaps better advised to go to nbc.com/30Rock and watch the video of Episode 202, titled “Jack Gets in the Game.” The setup to the joke starts about 9 minutes 20 seconds in.

Robert Carlock, an executive producer of “30 Rock,” said he came up with the idea as the writers mulled the breakup of the marriage of Tracy, played by the comedian Tracy Morgan. In the box of detritus that his wife delivers to him is the gold record from his recording of “Werewolf Bar Mitzvah.”