In real life, male mammals do not produce milk. Not even all female mammals produce milk — only post-pregnant mammals do.
The same usually applies to cartoon mammals, but there are some exceptions. In some cartoons, it is expected that any mammal will have the ability to produce milk, even if the mammal in question has been established to be, or otherwise evidently is, male. This will be treated as perfectly normal. Nobody will even hang a lampshade on it. Sometimes the trope is defied and discussed when characters think a male can produce milk, only for other people to point out that's not possible.
Sister trope to Egg-Laying Male. Subtrope of Animal Gender-Bender and Somewhere, a Mammalogist Is Crying. Compare Constantly Lactating Cow, for when female cattle are inaccurately depicted as being able to produce milk even when they've never been pregnant. May be in conjunction with Mister Seahorse. See also Non-Mammal Mammaries, for when a non-mammalian creature is depicted with milk-producing organs.
- When Kellogg's introduced their cereal milk bars, they came with a mascot, a cow named Uder. The problem is that this cow had a milk launcher affixed directly to its udder, leading to Viewer Gender Confusion until a later advert had Uder referred to specifically as a "he".
- Satellite Girl and Milk Cow: After turning into a cow, Kyung-chun can produce milk despite being male.
- Subverted in Into the Woods. Just like in the original Jack and the Beanstalk, Jack and his mother have to sell their cow because it's no longer producing milk, but in this version, Jack refers to the cow as a "he". But it turns out he was simply mistaken.
Jack's mother: It's a "she"! How many times do I have to tell you only "she"s can give milk?
- Discussed in Meet the Parents. Greg thinks any non-human animal can be milked regardless of sex, as long as it has nipples. Jack Brynes sarcastically asks Greg if he can milk him, since male humans have nipples too.
- Doctor Who: Strax, a member of the all-male clone race the Sontarans, was demoted to a nurse as a punishment for dishonoring his clone batch and one of the genetic modifications which came with said punishment was the ability to produce breast milk.
Strax: I can produce magnificent amounts of lactic fluid!
- House: In the B-plot for "Skin Deep", House is treating a man with couvade syndrome (sympathetic pregnancy) who is experiencing lactation among other symptoms. When his wife goes into labor, he gets contractions too. This gives House his "Eureka!" moment and allows him to diagnose his primary patient, a beautiful model with testicular cancer. What she didn't know was that she was genetically male but androgen insensitivity syndrome led her to develop externally as female. Her undescended testicles has been mistaken for ovaries in early scans. House handles this with his usual sensitivity and tact.
- Discussed in Buddha. When a woman points out a male dog's huge teats and says they look like they've been suckled, to which a man tells her they're useless, she then tells him that if a baby's mother dies, its father will begin to lactate.
Woman: I've read about cases, haven't you, where a woman dies and there's nothing to feed her baby, so the father puts the baby to his teat, and after awhile he begins to lactate, to produce milk, didn't you ever hear of that?
- The move Milk Drink in Pokémon was exclusive to Miltank which is an Always Female Pokémon until Pokémon X and Y introduced Skiddo and Gogoat. They are based on goats and can be female or male, making it this trope for the latter.
- Sam & Max: The Devil's Playhouse: In The Tomb of Sammun-Mak Maximus is transformed into a cow and Sameth milks him.
- The cows you rescue in Tribal Hunter are implied to be male, but are capable of being milked. Likewise the cow enemies you fight are clearly male based on their muscular build and their deep voice pitch, but their (hidden) udder balloons out massively once you force feed them enough eggs and they can also be milked in this state.
- Vampire Survivors' third stage takes place at a dairy plant overrun by minotaurs, and as their bestiary entry notes, "Yes, they're bulls. Yes, they're the source of most of the Dairy Plant's milk. No, you really shouldn't ask."
- Cows with Guns: The Great Cow Guru is referred to as "he" by the lyrics, yet squirts milk out of its udder at one point.
- Salad Fingers: In the third installment, Salad Fingers takes masochistic pleasure in stinging his body/fingers with nettles; about midway through, he is seen shirtless and caressing his nipple with the nettle, giving him some kind of orgasm which causes his nipple to lactate.
- Homestuck: Equius' lusus slash butler, the centaur Aurthour, is described as a male and has masculine traits such as a long mustache and a sculpted, distinctly not female chest, but also has a prominent cow udder and is implied to produce the milk he serves to Equius himself.
- Dragon Ball Z Abridged: While flying with Bulma, Yajirobe finds baby Trunks trying to suck his nipple. Bulma assures him that Trunks will stop when he realizes it's a dry well, only for Yajirobe to imply that being on an all-senzu diet resulted in him being able to lactate.
Yajirobe: Korrin likes it.
- Million Dollars, But...: One of the many prompts: you get a million dollars, but for the rest of your life you lactate. Cue a bunch of live action segments of the guys lactating at high pressure like a firehose.
"Is it good milk?"
"It's the best milk!"
- SMOSH: Discussed in "I HAVE KIRBY POWERS!" When Anthony inhales what he thinks is a woman (but is actually a crossdressing male prostitute named Bruce), he wonders why he didn't get any "cool girl powers" like being able to shoot milk out of his nipples.
- American Dad!: In "A Pinata Named Desire", Stan, while bragging about being better than Roger at everything, states he can wet nurse better than Roger — proven when wet patches appear on his shirt.
- Back at the Barnyard: Otis has been shown to be able to make milk in several episodes.
- In "Aliens!!!", when the animals find out that milk causes the aliens to dissolve, all the cows including Otis attach squirt guns to their udders and start blasting milk at the aliens.
- Implied in "Animal Farmers". After the farmer is injured, the animals have to do the farming themselves and Abby and Bessy do not want to attach the milking machine to their udders. Otis comes in and attaches it to his udder to demonstrate, saying that he's "seen the farmer do it, like, a hundred times".
- In "Brave Udders", Otis has a flashback to his childhood bully, Krauser Krebs, poking his udder and causing him to squirt milk on himself.
- Family Guy: In "Jungle Love", Peter says he's "excited for work like a dairy cow". Cut to a cow voiced by Danny Smith moaning in pleasure while being milked.
- High School U.S.A.: In "Janitor Day", Marsh discovers he can lactate.
- Phineas and Ferb: In "Does This Duckbill Make Me Look Fat?", Candace switches bodies with Perry the Platypus. While in his body, she is able to sweat milk. Apparently when she and Perry switched bodies they also switched hormones.
- The Simpsons: In "The Island of Dr. Hibbert", Ned Flanders gets turned into a cow-taur and asks Homer to milk him.
- Smiling Friends: Mr. Boss lactates and breastfeeds his son in one scene.
- Discussed in the South Park episode "Ginger Cow". Cartman keeps referring to the titular character as a 'he', yet also makes a joke about how its milk could be used to make ginger cheese. Cartman is either mistaken about its gender, or mistakenly thinks its udder is functional.
- SpongeBob SquarePants: Implied in "New Digs", where a transition happens and SpongeBob is suddenly holding a glass of milk, which he calls "a glass of warm snail milk". Was originally going to be played straight, with SpongeBob actually shown milking Gary, but the scene ultimately didn't make it into the episode because of the dirty implications.
- Teen Titans Go!: In "Justice League's Next Top Talent Idol Star", when Beast Boy turns into a cow for the talent contest, he is able to squirt milk out of his udder.
- The Venture Bros.: In the episode "Home Insecurity", when Dr. Venture and his sons are dropped into the panic room, Hank notices wet spots on Dr. Venture's shirt where his nipples would be. Dr. Venture states that "some men" "lactate". Hank thinks Dean does so as well after seeing the giant pee stain on his pants.