Invisible Holes

A character is subject to gunfire or sharp spikes, suffering no apparent injuries. But should he drink something or fall into water, the liquid will immediately pour out by small holes in his skin. Hilarity Ensues.

A classic gag predominately featured in animation. It has all the implications of terrible injuries, without all that massive bleeding and annoying death getting in the way of the humor. When it turns up in live action it's usually in a slapstick comedy, bonus points if it involves the undead or immortal "victim".

Examples of Invisible Holes include:

Advertising

Capri Sun's "Respect the Pouch" ad campaign had children mistreating the juice pouch, and suffering a fate relating to said mistreatment. One such commercial has a boy punching holes in the bottom of the pouch with a girl watching. He drinks from the straw and immediately starts leaking. The girl tries to block one hole.

Anime and Manga

In One Piece, Luffy mostly seems fine after having been impaled by Crocodile a few hours earlier (only wearing some bandages). When he resorts to drinking a lot of water to take advantage of Crocodile's weakness however, he promptly springs a leak.

Comic Books

This trope is referenced in one Archie Comics story, where Mr. Lodge goes to a barber for a shave. (Just roll with it) The barbar ends up cutting Lodge's neck several times, and when it's over, Mr. Lodge demands a drink to see if his neck leaks.

Film

As a reference to his cartoon-like powers, Jim Carrey in the film The Mask seems to survive being shot at by a squad of Mooks unscathed. He asks them smugly "Did you miss me?". He then takes a drink, sprouts several leaks, and declares "I guess not!".
Another live-action instance occurs in the film Carry On Henry, when a character who has been tortured in the iron maiden is offered a drink to steady his nerves.
- And in Carry On... Follow That Camel when Commandant Burger is shot by the Arabs.
Frank Cross's old boss Lew Hayward in Scrooged.
I think this has happened in a couple of Three Stooges shorts.

Live Action TV

Done in live action in an episode of Married... with Children. Al was rammed by a shopping cart (yes, a shopping cart) with spikes on the front during a shopping contest. At the end of the episode he is sitting relaxing, and when he takes a drink he sprouts several leaks.
A variation in Shooting Stars: after Bob stabs Vic with a pitchfork, we hear a hissing sound and Vic is able to produce woodwind-instrument-like noises by "playing" the holes.
This came up in the host segment of Mystery Science Theater 3000 episode Hercules and the Moon Men. Extremely tongue in cheek, of course.
Newt tries to invoke this to convince his parents not to make him run in the school election, telling them he was attacked by an echidna (or hedgehog, this troper forgets which). He rigged his shirt to squirt water like in cartoons. Predictably, it fails.

Western Animation

Happened several times to Tom in Tom and Jerry, with Tom being punctured by gunfire, garden implements and a baby woodpecker.
It also happens in a Droopy cartoon in which Droopy, as a sheepherder, catches a wolf trying to make off with his flock of sheep and repeatedly shoots his gun at him. The bullets all rush past the wolf, who calmly takes a drink of water and says, in a thick Southern accent, "Y'all missed me, sheepherder," and walks off, as the water flows out of holes made by the gun.
In Mexican Joyride, Daffy Duck goes South of the Border and has a bowl of chili, scoffing at how Mexican food is not so spicy. Immediately afterwards he has an inferno in his mouth, and he shouts, "It's burning holes in me!" A local sitting next to him says that he has eaten the stuff for years without any harm. He takes a drink, gets up to leave, and sure enough, water squirts from his body on the way out.
In the Tex Avery Wartime Cartoon Blitz Wolf, the holes are revealed not by water, but by light shining from behind the character.