Disney’s ‘Good Luck Charlie’: You’ve seen this family before

“Good Luck Charlie,” a new Disney Channel sitcom premiering Sunday, differs from other Disney Channel sitcoms in that, although the focus is reliably on the teen and preteen members of its cast, it is a family comedy. That is to say, the adults are less marginal to the action than they usually are in these things, though no less confused and ineffectual. In t(w)een TV, the kids always take care of the kids.

That notion is built into the very premise of the show. Because Dad and Mom (Eric Allan Kramer and Leigh-Allyn Baker) have to, or want to, work -- he’s in pest control, she’s a night nurse -- their three older children are enlisted to help look after the nearly brand-new one, 9-month-old Charlie (Mia Talerico), a “surprise.” So while there is no lack of typical teencom goofing and flirting, the core story is all about responsibility.

Created by Phil Baker and Drew Vaupen (Disney’s “Sonny With a Chance” and, from big-people’s TV, “Suddenly Susan”), it’s a professional sitcom from sitcom professionals whose opening half hour is neither awful nor exceptional. The jokes are efficient, the characters are variations on familiar types, the situations willfully arranged. But it does offer the contextually novel picture of a teenage girl taking care of her baby sister with a persuasive nonchalance and practical ease that transcends the strenuous comedy that surrounds it. I do not mean to celebrate an image of Flowering Womanhood here, only to put in a good word for a person acting like a person.

Bridgit Mendler is the girl, named Teddy, and she has been coming up through the Disney Channel ranks in the customary way, first as Nick Jonas’ crush in the first episode of “Jonas” -- that is as close to being Cinderella as you get in this particular world -- and then as a four-episode love-interest in “The Wizards of Waverly Place.” She is, like the other heroines who share her niche, sweet, smart and, you know it, a little sassy.

Teddy is making a video diary to help Charlie one day understand their “special family,” though it is no more special -- which is to say, no less weird -- than most TV families. They snipe at one another like old comics getting together for breakfast at the deli, but they all get along in the end.

Here is some of what they get up to in the first episode:

Dad drops the baby -- throws her into the air, actually, as he bumps down the stairs on his behind. (“Bob, you promised me you weren’t going to drop this one,” Mom says when she finds out.) Teddy’s woolly headed older brother PJ (Jason Dolley, another talented Disney Channel regular) impersonates a doctor. (“Are you sure you’re a real doctor?” the patient asks. “You look kind of young.” “Now you sound like my wife,” Dolley responds.) Needy younger brother Gabe (Bradley Steven Perry), who complains that no one is feeding him, crawls through the neighbor’s cat door to eat her food. Teddy wants to kiss her handsome study date, but life gets in the way.

As Charlie, Talerico, born in 2008, is so cute that she is billed above the actors who play her father and oldest brother. She has the seeming ability to be just the baby the scene requires -- though of course the number of takes, downtime or Disney magic required before she gets around to smashing herself in the face with a plate of bananas must remain a company secret.

robert.lloyd@latimes.com