“Stargate Atlantis” (8 p.m., Sci Fi) airs its 100th and final episode tonight. Series finales generally offer a chance to reunite cast members past and present and tie up a few loose ends. Occasionally, we get an “Oh, wow, Bob Newhart and Suzanne Pleshette in bed — I didn’t see THAT coming” moment, but those are so rare as to be memorable.

Tonight’s “Stargate” falls very much in the former category. Its title “Enemy at the Gate” sums up the situation. A renegade Wraith ship powered by hitherto untapped energy threatens Earth itself. This point of unparalleled peril provides a nice opportunity to reunite characters and fan favorites from across far-flung galaxies and several seasons. Will Earth endure? I’ll never tell. But sci-fi aficionados may feel let down by a plot device that seemed a tad dusty when “Independence Day” borrowed it from “Star Wars.”

• In other finale news, Wendy (Brooke Shields) juggles work and single-parenthood on the last original episode of “Lipstick Jungle” (8 p.m., NBC). Look for episodes of “Friday Night Lights” to air at this time beginning next week.

The cancellation of “Lipstick” points out once again the difficulties of launching and sustaining a drama or melodrama on network television. “Lipstick” would probably be a big hit on cable, where shows like “The Starter Wife” have thrived. “Lipstick” was based on the writings of Candace Bushnell, creator of “Sex and the City,” a show that was a hit on HBO and would probably never have succeeded on a network.

As “Lipstick” departs, Howie Mandel hosts the new series “Howie Do It” (7 p.m., NBC), a prank comedy show of the “Candid Camera” variety, the kind of show networks usually burn off during the summer.

• A modest summer hit for CBS, “Flashpoint” (8 p.m., CBS) returns. Like “Stargate Atlantis,” “Flashpoint” is a Canadian production.

Enrico Colantoni stars as Sgt. Gregory Parker, the unflappable commander of a SWAT team. In tonight’s episodes, they are assigned to protect a billionaire-turned-philanthropist (Colm Feore) whose less-than-idealistic past catches up with him in dramatic and unexpected ways.

Get used to Feore. He’s about to embark on an interesting role as America’s first husband (to a female president, played by Cherry Jones) on a new season of “24,” starting Sunday.

Tonight’s other highlights

• A mortal receives divine powers in the 2003 comedy “Bruce Almighty” (7 p.m., Fox), starring Jim Carrey, Jennifer Aniston and recent Kennedy Center Honors recipient Morgan Freeman.

• Adrian’s half-brother (Steve Zahn) escapes from lockup on “Monk” (8 p.m., USA).

• A convict from Don’s past returns with vengeance on his agenda on “Numb3rs” (9 p.m., CBS).

• “The FBI Files” (9 p.m., WE) looks at the Polly Klaas case.

• A sea lion’s demise smells fishy to Shawn on “Psych” (9 p.m., USA).

• Stars of the 1980s seek a second chance on “Confessions of a Teen Idol” (9 p.m., VH1).

Cult choice

Margot Kidder plays a set of identical twins with very different personalities in director Brian De Palma’s 1973 shocker “Sisters” (7 p.m., IFC).