The popular and engaging public-radio series “This American Life” (9:30 p.m., Showtime) and its host, Ira Glass, make their TV debut. Since 1995, Glass’ Chicago-based series has found a faithful audience with its hourlong presentations of first-person storytelling. Every show has a theme, like Honesty, Deception or Destiny, and each is presented and guided by Glass’ deceptively laid-back style.

Glass has a talent for finding the big ideas in the small details. My favorite “American Life” concerns a caustic and obscene message left on a college student’s answering machine by her own mother. Her roommate finds the withering missive hilarious and forwards it to a friend, and, before long, the tirade becomes an odd example of viral communication, making the student, and her somewhat chastened mother, unwitting celebrities on campus and beyond.

The first episode of the TV version of “This American Life” is called “Reality Check” but could just as easily be called “Be careful what you wish for.” A Texas rancher has his beloved bull cloned only to discover that bovine looks can be deceiving. And an improvisational street-theater group pretends to be a rapturous audience for an obscure bar band. Hoping to give the struggling musicians the greatest night of their lives, the troupe discovers that their hoax has made the band the laughing stock of the music industry.

Although Glass’ show has become appointment radio for many, I’m not sure how much impact this short series will have in television’s vast ocean. These vignettes might stand out more if they were a recurring part of a larger show, like Charles Kuralt’s “On the Road” segments on the CBS “Sunday Morning” series.

¢ “Penn & Teller: Bull—-!” (9 p.m., Showtime) returns for a fifth season. The celebrated team of illusionists skewers widely accepted beliefs and challenges politically correct concepts.

Think of John Stossel with more brains, a sense of humor, a penchant for obscenities and a little gratuitous nudity tossed in, and you’ve got “Bull—-!.”

Tonight’s episode explodes the notion of an obesity epidemic. Other topics to be tackled this season include Satanic conspiracy theories, the Americans with Disabilities Act and Wal-Mart and its critics.

Tonight’s other highlights

¢ The NCAA Basketball Tournament (6 p.m., CBS) continues.

¢ Check out three consecutive hours of “Eureka” (6 p.m., Sci Fi), the whimsical fantasy set in remote town peopled by the gifted and brilliant.

¢ World Championship Figure Skating (6:30 p.m., ESPN) from Tokyo, Japan.

¢ Earl and Randy go south of the border on an hourlong episode of “My Name Is Earl” (7 p.m., NBC).

¢ Betty plays along with a friend’s scheme on “Ugly Betty” (7 p.m., ABC).

¢ The 1998 documentary “Ku Klux Klan: A Secret History” (7 p.m., History) recalls the origins and rituals of the secret society.

¢ A car accident floods the hospital with victims on “Grey’s Anatomy” (8 p.m., ABC).

¢ A hefty golfer’s fatal heart attack was hardly inevitable on “Andy Barker, PI” (8:30 p.m., NBC).