Ed (8 p.m., NBC) reruns the one where Ed is reunited with his high school girlfriend and Carol tries to save the job of a veteran music teacher (Anne Meara). On a rerun of The West Wing (9 p.m., NBC), Mandy's embarrassing memo about the weaknesses of the Bartlet administration is leaked. Jiminy "welcomes" Conan O'Brien on Primetime Glick (10:30 p.m., Comedy Central).
It was 20 years ago today ... On Aug. 1, 1981, MTV made its debut with the Buggles singing "Video Killed the Radio Star"; in a short time, Music Television changed the rules of pop stardom and how music is made and marketed (for better and much, much worse). It also left its imprint on moviemaking, fashion, TV programming ("Beavis and Butthead," "The Real World," "Jackass") and pop culture as a whole. The 12-hour retrospective MTV20: Buggles to Bizkit (8 a.m. to 8 p.m., MTV) is a year-by-year look at MTV's evolution and changes in pop music. Then, Carson Daly and prehistoric VJs Martha Quinn, Nina Blackwood, Mark Goodman, J.J. Jackson and Alan Hunter host the three-hour birthday concert MTV20: Live and Almost Legal (8 p.m., MTV), featuring Mary J. Blige, TLC, Run-D.M.C., Jane's Addiction, Billy Idol and more (what, no 'N Sync?). Watch it and see your life flash before your eyes. Or you could tune in for State of the Planet With David Attenborough (8 p.m., Discovery Channel), a three-hour documentary about how humans are ruining the Earth. Hard to say which special is the more depressing way to pass an evening.
Braves at Cardinals (7 p.m., ESPN)
A's at Indians (7 p.m., ESPN2)
Rosie O'Donnell (syndicated) Donald Sutherland, the Corrs (rerun)
David Letterman (CBS) Lance Armstrong, Thora Birch
Jay Leno (NBC) Laurence Fishburne, Lucinda Williams
Politically Incorrect (ABC) Gilbert Gottfried, Sonny Girard
Conan O'Brien (NBC) Darrell Hammond, Jane Kaczmarek (rerun)
All times Eastern unless noted.