Kaitlin Olson isn’t a household name, but she should be. As a cast member of “It’s Always Sunny in Philadelphia,” which returns for its 12th season Wednesday, and star of the new Fox sitcom “The Mick,” which debuts Sunday, she’s a breath of polluted air. That’s a compliment.

For decades, crass acts on TV were reserved for the male of the species, from Ralph Kramden insisting the moon should orbit around his world to Homer Simpson shirking daddy duties for one more round at Moe’s Tavern. But “Inside Amy Schumer” and “Broad City” have shown that female leads can be just as sex-driven, self-centered and stupid as the boys.

They certainly owe a debt to “Seinfeld.” After reviewing the pilot episode, NBC insisted creators Larry David and Jerry Seinfeld add a woman to the mix. Enter Julia-Louis Dreyfus, who became one of the most celebrated comic actresses in TV history.

It would have been easy, though, for “Sunny” to under-utilize Olson. Of her four co-stars — all men — three created the series and write most of the episodes. The fourth is Danny DeVito.

But when it comes to the gang’s unethical schemes, Olson’s Sweet Dee is an equal partner. In the new season, she threatens to contaminate their neighborhood bar with anthrax unless someone serenades her with a Valentine’s Day poem. She lures a male stripper into borderline incest after he rejects her. She soils herself. Twice.

“That’s the darkest thing you’ve ever done,” says her twin brother, Dennis, after she celebrates a nasty bit of revenge.

Nothing Olson does in “The Mick” will top that, but she comes awfully close. We first meet Mackenzie Murphy creating havoc in a supermarket: crushing out a cigarette in a cantaloupe, shaving her armpits in the aisles and tossing back a beer the second her feet hit the parking lot.

Turns out that’s her good side.

Due to circumstances that make sense only in sitcomland, she’s suddenly put in charge of her sister’s three spoiled children, including a rebellious daughter who tries to take advantage by sneaking out. Dear Auntie’s solution: Mixing medication into the rebel’s drink that causes her to pass out at the dining table. How do you convince a teenage girl to stop having unprotected sex? Rig her pregnancy test and make a brazen move on her young boyfriend yourself.

The setup is beyond ridiculous, though, and treacle starts to seep in during an upcoming episode in which the newly formed family bonds over a belated party, albeit one that may be ruined by the birthday boy ingesting a heroin balloon.

“Sunny” hasn’t lost its nerve. In the opener, an electrical storm zaps the group into black characters who break into musical numbers inspired by “The Wiz.” But after 12 seasons, even innovative sitcoms feel like old hat. “Sunny” is no exception.

Perhaps “The Mick” is part of Olson’s escape plan, a chance to share her talents with the wider broadcast-TV audience. You may not wet your pants, but it’s a safe bet that her character will.