TONIGHT'S MUST-SEE

"That '70s Show" season-opener, 7 p.m., Fox. This show starts its eighth season, as goofy as ever. This hour is sometimes witless but occasionally quite funny. Last season, Hyde prepared to propose to Jackie — then changed his mind when Kelso showed up wearing only a towel. Tonight, everyone returns to Wisconsin, except for Eric (Topher Grace has left the series) and the new guy, who fell off the water tower one too many times. Now there's another new guy. A lot of marijuana has been sampled by Leo at the record store, by Eric's mom at home, and maybe even by the writers. They've created a loopy, goofy episode that ranges from clever to just silly.

"Rx for Survival: A Global Health Challenge," 9 p.m., PBS. For millennia, mosquitoes carried death. A 20th-century effort temporarily stopped them. But DDT was banned and mosquitoes developed resistance. Now birds have become key carriers. Tonight's second hour, "Deadly Messengers," provides a fascinating, global perspective.

OF NOTE

"Happy Days Reunion," 3:30, 8 p.m., Bravo. This cable channel is rerunning reunion shows. Tonight, it has "Happy Days" at 3:30 p.m., "The Carol Burnett Show" at 6, "Happy Days" again at 8 and "Burnett" again at 9:30. Still coming — "Beverly Hills 90210" at 6 p.m. Thursday, "The Cosby Show" at 6 p.m. Friday.

"E-Ring," 7 p.m., NBC. In the start of a two-parter, J.T.'s girlfriend is in a life-and-death situation. She can only give him a hint of where she is.

"The George Lopez Show," 7 p.m., ABC. Tired of having his mother at his house, George temporarily moves in with Ernie.

"Invasion," 9 p.m., ABC. A rerun of the terrific pilot. As a hurricane batters Homestead, Fla., there are family crises and conspiracy theories.

"Law & Order," 9 p.m., NBC. When a prisoner dies, a nurse practitioner is accused of trying an illegal form of sterilization. Her lawyer is Paul Robinette (Richard Brooks), an assistant district attorney on the show in its first three seasons.