Critic's corner
Wreckreation Nation 10 p.m., Discovery
Comedian Dave Mordal, best known for losing twice on "Last Comic Standing," travels the nation road-testing the extremely weird and ridiculously dangerous things people do for fun, among them school-bus tipping, swamp buggy derbies, and catfish grabbing. Tonight's premiere episode features lawn-mower racing and alligator wresting.
Shatner's Raw Nerve 10 p.m., Biography
The guy least likely to get his own talk show turns out to be the freshest interviewer out there: an empathic bully who manages to transport celebrity culture into the realm of the surreal. Tonight's episode is the one Trekkies have been waiting for: Shatner has his way with former costar Leonard Nimoy.
Blazing Saddles 8 p.m., AMC
Mel Brooks's sidesplitting sendup of Hollywood westerns, co-written with Richard Pryor.
Nip/Tuck 10 p.m., FX Without fail, the guiltiest of pleasures. Earth's Black Hole 8 p.m., History Channel A personal programming favorite: the Bermuda Triangle. Scrubs 9 p.m., Channel 5 Courteney Cox materializes as Kelso's replacement in the season 8 opener. 