You know that old show business saying, never work with dogs or space aliens. A couple of new sitcoms debuting Wednesday defy the conventional wisdom with mixed results.

NBC’s Animal Practice sounds insufferably cute: a romantic comedy set in a veterinary hospital, where you can alternate kissy-face stuff with kittens pushing around balls of yarn until even vegans are plunging forks into their eyes. Stunningly, that’s not the case. Instead, it’s more like M*A*S*H* for the four-legged, a subversive and perversely funny workplace comedy.

In place of Trapper John, we have Dr. George Coleman (played by Justin Kirk, who just finished eight years as Mary-Louise Parker’s crackpot brother-in-law on Weeds). Coleman’s contrast view of animals and humans is summed up pretty well by his reaction when one of his patients, a python, starts strangling a nurse: He runs to get his cellphone to snap a picture.

That puts him at odds with the Hot Lips Houlihan of Animal Practice, administrator Dorothy Crane (JoAnna Garcia Swisher, Better with You), who takes a dim view of Coleman’s use of the animals to pick up girls or win bets. Acting as bookie on the latter is the scene stealer of Animal Practice, a hilariously venal Capuchin monkey known as Dr. Rizzo, doubtless a homage to Dustin Hoffman’s hustle-a-minute character in Midnight Cowboy.

The rest of the two-legged cast, including Tyler Labine of Reaper and Bobby Lee of the Harold & Kumar movies, brings considerable comic chops to Animal Practice as well. And how are you not going to love a show in which the patients include a penguin with acute gastrointestinal distress and the cast runs down the hallways shouting things like “Bengal tiger giving birth!”?

The Neighbors, one of only two new sitcoms in ABC’s fall lineup, has moments like that, too, but not nearly enough of them. Lenny Venito and Jami Gertz star as a married couple moving into a suburban subdivision who discover their new neighborhood is entirely populated by aliens, and not the kind who walked across the border from Mexico.

But, happily, also not the kind usually played by Sigourney Weaver. Despite their addled efforts to imitate Earthlings, which include obsessively listening to old Ink Spots records and naming their kids things like Dick Butkus and Reggie Jackson, the only really yucky thing about the space visitors is their occasional reversion to their original form (looking a bit like Dr. Seuss’ Grinch), which includes an explosion of green slimy stuff.

In short, The Neighbors closely resembles the old Conehead sketches from the early days of Saturday Night Live. And it’s not without laughs, especially when the exuberantly funny Gertz, one of the most underrated comedians of her TV generation, is on screen. But there’s a reason the Coneheads did well as a skit and not as a movie. The joke is already showing signs of wearing thin by the end of the first episode. Land Shark, anybody?