We’re just a few weeks away from the time when networks announce their new programs and fall schedules. This also marks the sad time when a few fading favorites get the ax. Will “Dharma & Greg,” “Touched by an Angel,” “Ally McBeal” or “Spin City” reappear next fall? Stay tuned. The series finales for some shows have already been announced. “X-Files” will take its final bow on May 19. “Once & Again” will wrap up its emotional loose ends on April 15.

Some fans can’t sit back and watch the screen fade to black. In 1967, “Star Trek” fan BJO Trimble rallied thousands to write letters to NBC and saved the cult series from being scrapped after its first season. Trimble’s efforts were so effective that “Trek” creator Gene Roddenberry hired her to coordinate fan relations.

Just imagine if Trimble had access to the Internet back then. The web is overrun with passionate television fans who are not shy about showing support for their favorite shows. For example, the Web site http://www.petitiononline.com is host to thousands of petitions on subjects ranging from politics to pop culture. Five of the site’s top 25 petitions concern TV shows. Nearly 26,000 fans asked ABC not to cancel “Once & Again.” A plea for a “Season 4 For “‘Roswell”‘ gathered 22,007 cyber-signatures. Were you surprised when Nickelodeon canceled the cartoon “Invader Zim”? Fifty-two thousand fans have already expressed their outrage. Cartoons seem to animate a lot of furious fan activity.

Some networks are listening. You can download a letter from a CNN executive responding to a petition, signed by 5,627 people, “Protesting the Negative Portrayal of Muslim Women on CNN.” Gosh, that’s only one-tenth of the number who want to save “Invader Zim.”

 The joyously silly new comedy “Greg the Bunny” (8:30 p.m., Fox) takes some shots at “identity politics” in a very funny episode. Greg alienates the cast of “Sweetknuckle Junction” after he falls under the spell of a radical puppet rights activist and begins to demand a more positive portrayal of puppet culture (AKA “puppism”) on the show.

 Hal Holbrook guest stars as an assistant secretary of State on a repeat of “The West Wing” (8 p.m., NBC). He’s a natural for this political series. Holbrook has been acting in Washington-based dramas since “West Wing” creator Aaron Sorkin was in grade school. He portrayed “Deep Throat” in the 1976 drama “All the President’s Men.”

Tonight’s other highlights

 Scheduled on “60 Minutes II” (7 p.m., CBS): an ambitious father tries to mold the next Tiger Woods.

 Sandra Bullock guest stars on “George Lopez” (7:30 p.m., ABC).

 Bernie’s radio talk show patter gets him in trouble with Wanda on a repeat “Bernie Mac” (8 p.m., Fox).

 Formerly state-controlled economies face shock treatment on “The Agony of Reform,” part two of the three-part series “Commanding Heights: Battle for the World Economy” (8 p.m., PBS).