Two once-promising NBC series wrap up their seasons tonight. It’s never a good sign when a show folds up its tent before the May sweeps period. The early exits for “Chuck” (7 p.m., NBC) and “Heroes” (8 p.m., NBC) reflect the difficulty of competing against “Dancing with the Stars” (7 p.m., ABC), particularly as it enters its final stretch. On the other hand, CBS does just that with its quartet of popular comedies.

This marks a dismal end for a bad year at NBC. Its fall 2008 schedule offered a small basket of new shows and viewers proceeded to drop the basket. Few watched and fewer recall “My Own Worst Enemy,” “Crusoe,” the new “Knight Rider” or “America’s Toughest Jobs.” “Kath & Kim” seemed destined to be remembered as the worst new sitcom of the year until “Parks and Recreation” came along. “Lipstick Jungle” withered away, and “Life” developed a small but devoted following. I thought “Kings” looked promising, but not enough people gave it a look. It premiered on Sundays, and was moved to the Siberia of Saturdays, and then it was yanked from the schedule completely. It’s supposed to return for a summer airing, a time when only the most devoted fans will remember to watch.

Tonight’s “Chuck” ends in true season-finale fashion, with the scheduled wedding of Chuck’s sister, Ellie, and her boyfriend, Awesome. Too bad Chuck is otherwise engaged on the really big day.

It’s best not to reveal too much about the “Heroes” finale. But it’s safe to say that when you’ve got a shapeshifter (Syler) at work, it’s going to be difficult to know who’s on first, or, for that matter, who’s who. Hiro discovers that his time-stopping talents may have serious repercussions. Written by series executive producer and creator Tim Kring, the episode offers some interesting resolutions and departures for key characters. Short of definite word on the fate of “Heroes,” this could work as either a great chapter ender or a murky series finale.

Tonight’s other highlights

• Unheard noises push a deaf teenager into a coma on “House” (7 p.m., Fox).

• Left for dead at 2:59 a.m., Jack manages to interrogate a key suspect during the 3 a.m. installment of “24” (8 p.m., Fox).

• “We Shall Remain: American Experience” (8 p.m., PBS, check local listings) recalls the 1838 forced relocation of Cherokees known as the “Trail of Tears.”

• “12 Notes in Real Time” (8 p.m., Documentary) continues the “Jazz in the Present Tense” series, a celebration of active and contemporary musicians.

• George Clooney stars in the 2002 remake of the 1972 cult Soviet sci-fi film “Solaris” (8:45 p.m., IFC).

• A TV dating show becomes a crime scene after an unscheduled elimination on “CSI: Miami” (9 p.m., CBS).

• Allison’s stalker intrudes on her visions on “Medium” (9 p.m., NBC).

• A victim’s body is discovered in a vat of motor oil on “Castle” (9 p.m., ABC).

Cult choice

Guy Williams (“Lost in Space”) stars in the 1963 fantasy “Captain Sindbad” (5 p.m., TCM).

Series notes

Sheldon prepares for a big weekend on “The Big Bang Theory” (7 p.m., CBS) … Georgina returns after major changes on “Gossip Girl” (7 p.m., CW) … Text messaging a prank on “How I Met Your Mother” (7:30 p.m., CBS) … Matchmaking madness on “Two and a Half Men” (8 p.m., CBS) … Nick Lachey appears as himself on “One Tree Hill” (8 p.m., CW) … A big announcement on “Rules of Engagement” (8:30 p.m., CBS).