What’s Worth Watching: ‘Agatha Raisin’, ‘Unreal’, ‘Supergirl’ and more.

Agatha Raisin (Premiering on Acorn TV): A seasoned scene-stealer grabs the spotlight as tart, smartly funny Ashley Jensen (Ugly Betty, Extras, Catastrophe) graduates to center stage, playing the endearingly silly title character of a delightful comedy-mystery series based on M.C. Beaton’s books. Bossy and saucy, snoopy and snarky, glamorous former P.R. maven Agatha finds a new calling as amateur detective, invariably outsmarting the bumbling local bobbies in the gleefully twee village she has decamped to from London. The cases tend to be slight and offbeat: In the movie-length opener (followed by eight episodes streaming next Monday), a poisoned quiche is the culprit. The quirkiness comes from the top down, embodied by this busybody who ropes her new neighbors, including the hunk next door, into helping her solve crimes. Jessica Fletcher would be so proud, and amused.

MTV Classic (launched at 6 am/5c): Say goodbye to VH1 Classic, as the channel rebrands itself to celebrate the legacy of MTV on its 35th birthday. It begins with MTV Hour One, a replay of MTV’s very first hour of actual music programming (remember that?), back in 1981. (If you miss the first hour, it will be replayed at noon/11c.) The first afternoon will be devoted to a Total Request Live retrospective, The TRL Decade, followed by an MTV Unplugged marathon and a prime-time lineup including MTV fan faves Daria, Beavis & Butt-head and Aeon Flux. Those of us old enough to remember the “I Want My MTV” crusade may think of this as a recognition that some fans “Want Our MTV Back (the way it used to be).”

UnReal (10/9c, Lifetime): This dark soap-within-a-fake-reality-show has experienced some inevitable but not unearned backlash in its over-the-top second season. Criticism intensified in the wake of a police shooting of a black character (the “suitor’s” BFF) who vanished immediately afterward so the focus could fall instead on the mental breakdown of the incident’s architect: poor, broken Rachel (Shiri Appleby). Her taped confession of past misdeeds last week to boyfriend/disgraced show-runner Coleman (Michael Rady) fuels this week’s conflict, as he tries to convince Rachel to take down the evil Quinn (Emmy-nominated Constance Zimmer) and faux dating show Everlasting, which in a real world would have been canceled or suspended already after all of these shenanigans. Even with its flaws, I’d rather watch UnReal than the three-hour finale of ABC’s The Bachelorette (8/7c), during which Jojo chooses between Jordan and Robby, followed by an After the Final Rose recap.

Supergirl (8/7c, The CW): Leaping between networks at a single bound, the spunky super-heroine (Melissa Benoist) sets up shop at her new digs, swapping CBS for the sister channel that overflows with DC Comics adaptations. In advance of the second season, which begins Oct. 10, Supergirl will air back-to-back episodes on Mondays, starting with the soaring pilot and the second episode, in which Kara has to overcome her, and National City’s, doubts about her abilities. Long may she fly.

Inside Monday TV: Lots of documentaries on the schedule, including Spike TV’s I Am JFK Jr. (9/8c), a glowing bio of the too-short-lived president’s son. . . . Maverick filmmaker Alexandra Pelosi is back on HBO with the timely Meet the Donors: Does Money Talk? (9/8c), in which she talks to high-rollers who invest in candidates on both sides of the political spectrum, as well as those who are emptying their deep pockets to try to reinstate campaign finance reform. . . . PBS’s POV presents the late Albert Maysles’ acclaimed biographical portrait of 90-something fashion icon Iris Apfel in Iris (10/9c, check local listings at pbs.org). . . . More reality TV than documentary, NBC’s Running Wild With Bear Grylls (10/9c) opens a new season with Nick Jonas roughing it with the naturalist in the icy wilds of the Sierra Nevada Mountains.