Debbie Reynolds returns for “Halloweentown High” (7 p.m., Disney), the third cable fantasy movie about the enchanted Cromwell family, who pass as “normal” in a human world but are really part of the enchanted realm of fairies, elves, leprechauns, dragons, you name it.

Reynolds portrays the slightly befuddled grandma, Aggie. Kimberly Brown is the teen star of these proceedings. She’s Marnie, the precocious daughter of a witch mother and mortal father. So mortal, in fact, that he has died.

Marnie talks a council of wizardly elders into a student-exchange program between her “normal” high school and the enchanted population. The new students, including a witch, warlock, troll, werewolf and ogre, don human costumes to fit in, but soon find themselves coping with post-pubescent peer pressure and pecking orders.

But Marnie has more than Homecoming dances to worry about. The ancient Knights of the Iron Dagger have gotten wind of her plan. They are dedicated to destroying everything magical, and have been waiting a millennia or two to get the job done. They’re clever, too, particularly the knight who takes the shape of a handsome teenage boy.

While thoroughly silly, “Halloweentown” is that rare TV film that will appeal to the under-12 set as well as fans of Debbie Reynolds, one of the last great survivors of the Hollywood studio system.

• Archer and crew are transported back to Earth in the 1940s as the Nazis invade the United States with the help of an alien race on the season premiere of “Star Trek: Enterprise” (7 p.m., UPN).

Kirk and Spock took on the Nazis, too, on the “classic” “Trek” series. As for aliens aiding Hitler, that reminds me of the old “Saturday Night Live” bit called “What If?” that pondered the fateful question, “What if Superman (make that Uberman) was on Hitler’s side?” But “Saturday Night Live” is a comedy, whereas the tired “Star Trek” franchise is sadly descending into farce.

• Charles Gibson moderates the second of three Presidential Debates (8 p.m., ABC, CBS, Fox, NBC, PBS, CNN, Fox News, MSNBC). The event is broadcast live from Washington University in St. Louis, Mo.

Tonight’s other highlights

• Tilling the soil and tending to seeds on “Joan of Arcadia” (7 p.m., CBS).
• Scheduled on “Dateline” (7 p.m., NBC): a weight loss challenge.
• Major league baseball division playoffs (7 p.m., ESPN).
• The 1998 documentary “The Farm: Angola USA” (8 p.m., A&E) chronicles life in a Louisiana penitentiary.
• The hip-hop history series “And You Don’t Stop” (9 p.m., VH1) concludes with artists who have emerged since the 1990s, including Eminem and OutKast.

Late night

Director Barry Sonnenfeld appears on “Late Show with David Letterman” (10:35 p.m., CBS) … Jay Leno greets Tom Green, Ciara and Petey Pablo on “The Tonight Show” (10:35 p.m., NBC).