TONIGHT'S MUST-SEE

"What About Brian," 9 p.m., ABC. It's Adam and Marjorie's wedding day, leaving Brian in his usual state of indecision. The night before, Adam partied with a stripper and Brian got a surprise romantic visit from Marjorie. Now the wedding proceeds and Brian — as always — dawdles. Beautifully filmed and warmly acted, this show still seems doomed. Its fragile plot line keeps being stretched wildly.

OF NOTE

Baseball, 2 p.m., Fox. It's the fifth game of the best-of-seven National League series between the New York Mets and the St. Louis Cardinals. If one team sweeps in four games, Fox will insert reruns of "Prison Break" and "Justice."

"How I Met Your Mother," 7 p.m., CBS. Barney has a rare, good-hearted moment, letting Lily share his apartment. Then he pulls her into one of his schemes.

"The Class," 7:30 p.m., CBS. Wonderful things happen when the sweet Ethan and the acidic Kat are together. Tonight, she wants him to let loose by grabbing too many free samples of frozen yogurt; for him, that's an adventure.

"Two and a Half Men," 8 p.m., CBS. Earlier, Ryan Stiles ("The Drew Carey Show") played Dr. Melnick. Now he's engaged to Alan's ex-wife, Judith. Charlie and Alan are eager to make sure they marry.

"Heroes," 8 p.m., NBC. It has occurred to Hiro that his ability to manipulate time might be helpful in Las Vegas. Meanwhile, Nathan is also in Vegas — and Claire is in one of Isaac's creepy paintings.