In video games, what's the in-universe explanation for taking damage after touching enemies?

[Omnium Ultimatus]

For example, do goombas kick Mario in the groin when he touches them?

 

[Vingle]

No, he's just a snowflake like soccer players whining by the littlest of touch.

 

[Dysnomia]

They weren't vaccinated.

 

[Megaroad 2012]

cooties

 

[Crunchy Oats]

Maybe electrocution?

 

[zero-who]

• In the 3D games, the Goombas tackle Mario and knock him down.
• Don't remember what the Koopas did, but in Brawl's Subspace Emissary, they headbutted you.
• Piranha Plants and Chain Chomps bite.
• Bullet Bills, Hammer Bros, Spinies, Thwomps, Bob-ombs, fireballs/bars, you can probably guess why you take damage from them.
• Cheep Cheeps I think bite. They're probably like a territorial fish, like a big cichlid or something. There's also games where they jump out of the water, and if you've ever seen the videos where someone goes fishing for carp and smacked in the head by one, you know how that could hurt Mario.
• Bloopers, I imagine would behave similar to Humboldt squid or a particularly nasty octopus.
• Boos attack Mario's soul directly.
• Bowser, just look at his Smash moveset.

 

[Kosher Dill]

The original intention was that if the Goombas caught Mario, they would handcuff him, jail him, and put him on trial for crimes against the Koopa King. This was one of Miyamoto's ideas that ended up on the cutting room floor due to the limitations of the Famicom, as well as being able to ride a rocket or a dinosaur.
The dinosaur, of course, eventually made it in for "Super Mario World".

 

[Klaptrap]

Ebola

 

[Professor G. Raff]

Severe autism causing your character to violently hurt themselves in the struggle to avoid physical contact with another living being.

 

[GhostButt]

In Mario Clash there is a frame of animation that implies that they bite you if you are too close rather a touch occurring.

 

[Gravityqueen4life]

they have aids.

 

[Cloaca Rimjob]

They're chocolate land dwelling jellyfish

 

[MrTroll]

Mario is clearly a hemophiliac in every part of his body except his ass.

 

[Least Concern]

I think the real question is, why does touching a mushroom cause Mario to double in height (and the mushroom to disappear)?

My working theory is that the mushrooms (and flowers) in the Mushroom Kingdom are extremely psychedelic and only make Mario feel like he's twice as tall (and can throw fireballs), and every mainline Mario game is in fact a psychedelic dream. Mario's a shroom junkie. I'm sure I'm not the first one to come up with this theory.

 

[Kosher Dill]

I think the real question is, why does touching a mushroom cause Mario to double in height (and the mushroom to disappear)?

In a minute or two the Caterpillar took the hookah out of its mouth and yawned once or twice, and shook itself. Then it got down off the mushroom, and crawled away in the grass, merely remarking as it went, “One side will make you grow taller, and the other side will make you grow shorter.”

“One side of what? The other side of what?” thought Alice to herself.

“Of the mushroom,” said the Caterpillar, just as if she had asked it aloud; and in another moment it was out of sight.

 

[Tanuki Mixed Nuts]

It's the emotional damage of coming into contact with someone who doesn't love you. It's why holding hands when unmarried is dangerous.

 

[Tackleberry]

You all got this wrong. Mario is the ultimate beta male simp lefty. The only thing that makes him feel big are hard drugs and flowers. He's a furry, plays shitty music on his flute, and is always trying to get the girl away from the alpha male.

That being said, the goombas could be doing something as simple as calling him a faggot when he approaches.