"If you love something, set it free. If it comes back, it's yours. If it doesn't come back, it was never yours to begin with. But if it just sits on your couch, eats your food, watches your TV, and uses your phone, and doesn't seem to realize or care that you set it free, you either married it or gave birth to it."
—A parodic twist on a well-known proverb
This is where in a married couple, the husband is child-like and the wife is like a parent to him except that she can quite easily provide him sex. Sometimes, the wife may talk about feeling like she really does have one more child than the number of children they have, and guess who the extra is? Ironically, her job of child care may be made easier by the husband being able to connect to their children more effectively.
Sometimes, this is part of a Closer to Earth setup, with a Bumbling Dad. He may also be a Henpecked Husband, or he may just have a penchant for causing wacky hijinks that his wife must resolve. Sometimes, the husband is perfectly angelic or a hard worker, or a mixture of the two, and the wife is simply motherly with no shallow motives.
A rather awful Double Standard (not owing to sexism, but more as a curious after-effect of All Girls Want Bad Boys —most of all from said boy's slacker side—); the notion of a girlish wife in need of control and protection by a fatherly husband rarely appears today but this one persists. There are Unfortunate Implications on both sides - men are told that they're useless and incompetent, at least in the realm of family life, and should really just let their wives take charge; women are told that they can't expect their husbands to act like grownups and should just resign themselves to always having to be the boring, responsible killjoy in the family.
In Dragon Ball, Chi-Chi treats her husband Son Goku very much like this. However, it could be subverted, as the fact that Goku is a phenomenally powerful alien Martial Artist makes this relationship look more equitable than most other examples — Chi-Chi "takes care" of Goku at home, Goku "takes care of her in return"... by saving the world on a regular basis. To say nothing of when Goku actually does get de-aged to a child.
Baron and Baroness Bomburst in Chitty Chitty Bang Bang. She buys the man toys, for God's sake, and coos over him as if he were a precocious, temperamental infant. (Which, admittedly, he totally acts like.)
Taken to a rather Squicky extreme in Merlin's Shop of Mystical Wonders: The Jerk Ass critic in the first story, as a result of a spell gone wrong, turns into a baby, giving his infertile wife the son she could never conceive. Needless to say, when this movie was featured on MST3K, this did not go un-mocked.
Mike: Oh, good, now she has to raise her horrible husband!
Crow: That's what most wives think they do, anyway.
When the doctor in Blindness goes blind, his wife ends up treating him more like an infant than a spouse anymore, and it repulses him.
Most modern sitcoms. (50 or 60 years ago, however, you were more likely to see the reverse.)
Desperate Housewives has Tom and Lynette Scavos. Lynette often has to play the bad guy and suffer through being the disciplinarian while Tom is the cool Hot Dad.
Friends: There was an in-universe joke that Monica was the adult and Chandler the child, but the truth was that Chandler was equally likely to be the adult to Monica's child. It usually depended on what joke the episode was going for.
How I Met Your Mother has Lily and Marshall. There's even one scene where Ted and Marshall are standing in front of Lily with their heads bowed like little children getting punished and saying "Sorry, Mom Lily" together.
This one goes back and forth and around, though, as Lily is often shown to be immature and occasionally infantile as well as the others. Taken to an extreme in one particular episode where Lily is convinced that Marshall is ready to raise a child because he was able to take care of her when she was drunk and acting like a child. The same episode was also one of many to point out that Ted is basically already a dad without kids (or a wife, for that matter).
It even expands to include Ted in an epsiode where he briefly moves in with Robin and Marshall and Lilly realize he owned all the useful stuff like towels and he bought all the food.
The Cosby Show, though Cliff Huxtable is not a Bumbling Dad, and this one possibly isn't an example of Closer to Earth; Clair Huxtable was more practical but not really morally superior, and in fact was sometimes *indrawn breath* wrong.
Debra and Ray Barone in Everybody Loves Raymond fit this to a tee in the mid-to-later seasons of the show. Ray is actually more of a nebbish. In the earlier seasons of the show, Raymond was portrayed as being rather clever and witty, at one point even winning a national award for his writing skills. In the later seasons, he was seemingly dumbed down to make Debra look better by comparison, all so that the show could more easily shill Debra and use this trope.
Believe it or not, the parents of the Toad family in Westmost house in Toad Town of Paper Mario manages to fit this trope. The wife mentions in one of her conversations that she feels like she has three children.
Matsu to her somewhat slow but endearing hubby Toshiie in Sengoku Basara.
Family Guy: Lois and Peter Griffin. One episode even had a scene where he was refusing to brush his teeth and she would've had to do it for him if they hadn't heard burglars breaking in at that moment.