Chris O'Dowd and Tom Bennett

It can't be easy to learn that one's ancestor is a literal horse's ass. But sad-sack Londoner Tom Chadwick takes such news in stride, again quite literally, as he acquires his great-grandfather's horse costume from a long-ago pantomime show, and after trying the rear end on for size, adds it to his collection of quirky family keepsakes.

HBO's droll-to-the-point-of-precious and occasionally delightful Family Tree (Sunday, 10:30/9:30c) follows Tom on an offbeat personal odyssey into his cloudy lineage. "In our clan, family is what disappears when you're not looking at it," says his retired dad, who keeps busy inventing useless objects like a fan for shoe trees. The dad is played by Michael McKean, who like the rest of the cast often talks directly into the camera, mock-documentary/improvisation style. The casting and the format are two of the more obvious signs that Tree is a Christopher Guest production.

Another tip-off: The show's tone of gentle, warped whimsy, embodied by Chris O'Dowd's warmly forlorn star performance as Tom, unemployed and emotionally adrift, who begins his quest when bequeathed a trunk full of artifacts by a great-aunt he can't really remember. Photos, clippings, articles of clothing all serve as clues propelling Tom into unraveling mysteries of the past, eventually leading him across the pond to the U.S. Along for the ride: an oafish best mate played by Tom Bennett, who seems to be over-channeling the mischief of Ricky Gervais, and an oddball sister (Nina Conti) who speaks bitter truths through a monkey hand puppet, a startling gag that quickly loses its novelty.

Tree bears comic fruit with its honesty and humanity, but unlike the cheesy old-school sitcoms we see the older generation enjoying (all created specifically for this show), it's not intended to be a laugh riot. Like many HBO half-hours, this is a slow, slow burn to get to a payoff. The smiles here are of recognition that even the most ordinary families can have wonderfully strange roots.

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FINALLY MAD FOR MEN: If the subject is delayed gratification, this season's champ is AMC's Mad Men, which after a month of ponderous, self-consciously pretentious and clumsily "relevant" episodes finally roared to life last week, with the surprise merger of boutique agencies SCDP and CGC into an upstart powerhouse. "Nice to have the old team back together," Don Draper glows in the cryptic-as-usual trailer for this week's episode (Sunday, 10/9c) as Peggy Olsen returns to the fold — which could make for some interesting dynamics, seeing how she's been channeling Don lately as she came into her own authority at the rival-now-partner firm. As the new version of Sterling Cooper Draper Pryce "tries to placate competing clients" (which is as specific as AMC's tease gets), we're settling in for what we hope is a satisfying back half of the sixth season.

WELCOME BACK: Which of her classic characters will Kristen Wiig reprise when she returns to her launching pad of NBC's Saturday Night Live (11:30/10:30c) this week as guest host? Can't wait to find out. (My personal favorite: Sue, who busts a gut any time she tries to keep a secret. My personal peeve: the mischievous Gilly.) ... Another name that gets instant attention: George R.R. Martin, who wrote the books on which HBO's Game of Thrones is based, and who penned this week's episode (Sunday, 9/8c), in which we catch up with Daenarys, who was sadly missing from last week's otherwise spectacular episode.

FINALE FEVER: As I write this, it has yet to be determined if Friday's episode of CBS' Vegas (9/8c) is the season or, quite possibly, series finale. In any case, it's a case of strange bedfellows as Sheriff Lamb and mobster Savino team up to take down the creep (Michael Ironside, a reliably odious villain) who put lovely Elizabeth in the hospital. In potentially happier news, Deputy Jack prepares to propose to Mia. Why let a little thing like killing her gangster father get in the way? ... Among other significant finales: On CBS' already renewed Blue Bloods (Friday, 10/9c), patriarch Frank deals with a personal loss as the family rallies to go after a gang leader who killed someone close to home. ... From the "that's still on?" files: Fox bids adieu for good to Touch (Friday, 9/8c) as Martin races to save Jake and Amelia from the evil Aster Corps. If it ends in a cliffhanger, blame the producers. If they didn't know this was coming, they're the ones who are touched. ... After Wednesday's wrenching blindside of Brenda, CBS' Survivor heads into its two-hour finale (Sunday, 8/7c) with one more twist: an 11th-hour medical emergency. We don't know who will make the final three, but if either underdog "amigo" Eddie or the crafty nerd Cochran are still in play, they have my vote. As usual, a reunion show follows, yet one more occasion for Dawn to burst into crocodile tears. ... ABC's Once Upon a Time wraps its second season (Sunday, 8/7c) with Storybrooke preparing itself for annihilation. Yeah, right. Not when a spin-off is right around the corner. ... In a two-hour finale of ABC's Revenge (9/8c), we're promised someone will die, one hopes with more impact than when Faux-Manda left this mortal coil earlier this season.

ALL ABOUT MOM: It's Mother's Day weekend, but not a particularly happy one for some TV moms. In the Hallmark Channel movie Beverly Lewis' The Confession (Saturday, 9/8c), Switched at Birth's Katie Leclerc plays an Amish lass who leaves her community to search for the birth mother (Sherry Stringfield) who put her up for adoption. It's not such a smooth reunion when she discovers her biological mom is not only dealing with terminal cancer but is being victimized by her husband (Adrian Paul), who's perpetrating a fraud by introducing a fake "daughter" into the picture (played by Julia Whelan, of whom we've seen far too little since Once and Again). ... Lifetime draws from the female-in-jeopardy well with Dangerous Intuition (Saturday, 8/7c), in which Battlestar Galactica's Tricia Helfer plays a divorced career woman who begins having terrible nightmares of motherly intuition when she's forced to share custody of her daughter with an unstable stepmom (Estella Warren). ... Never one to miss an opportunity to shine a dark spotlight on a happy occasion, Investigation Discovery marks Mother's Day with the special Evil In-Law (Sunday, 9/8c), in which wicked mothers-in-law prove that three in a marriage is an often deadly crowd.

MOTHER NATURE: When Discovery and the BBC get together for a nature special, you can bet the visuals will be memorable. So it is with Great Bear Stakeout (Sunday, 9/8c), in which crews lived among grizzlies in the Alaskan wilderness for the entire five-month season between hibernations. ... Our 49th state certainly is popular on TV these days. National Geographic Channel explores the rugged terrain in a new competition series, Ultimate Survival Alaska (Sunday, 10/9c), with survivalists dropped into the wilds with only the packs on their backs, given 72 hours to make their way to a finish point. They're not racing for money, just for pride in being able to survive the conditions. Take that, Jeff Probst.

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