Huh. Always thought unicorn horns are rigid like fingernails.

@Background Pony #2D3B  
Besides the joking nature of that headcanon, I could add more humor by pointing out he was the only stallion in a room with 5 cute mares.

@Stotter  
Party Favor wasn’t doing any magic when he punctured an inch or so of wood with his horn.

@Background Pony Number 17  
Random headcanon: Unicorn horns get more rigid when in use. Like something else. wink wink nudge nudge

History has it that so-called “unicorn horns” were prized possessions for kings…until they were discovered to have really come from narwhals.
 
To answer the question of what a unicorn horn is made out of, I tried doing some “research” on this…and came across quite a few opinions including “cellulose fiber mixture and graphite”, keratin (the same stuff fingernails are made out of), ivory (think elephant tusks) and “alicorn” which apparently refers to both the horn of the unicorn and the magical substance the horn is made of.
 
So there you have it: the simplest explanation is unicorn horns are made of alicorn…which for all we know of the fantasy world could very well be a magical mixture of cellulose fiber, graphite, keratin and ivory.

@Jackarunda  
or cartilage

I’m sure they’re closer to bone, perhaps somewhat flimsy since Sweetie Belle flicked Rarity’s (it had a much higher frequency of oscillation, suggesting a more rigid structure than shown here), but this is Discord. Anything he touches instantly takes on whatever traits required in order to be funny.

Well….we can’t use this as a judge of the texture and flexibility of unicorn/alicorn horns since Discord is doing that.

Oh Twilight. You know you kind of like it.

@Background Pony Number 17  
The horn isn’t bending at all there.

@Background Pony Number 17
 
But see, Rarity’s horn here behaves more like a piece of wood. In this upload, Twlight’s horn behaves more like a piece of rubber.

@Litrojia  
 
You’re right, it has.

I guess we all can say that it’s Discord making Twilight’s horn so bendable XD
 
This part was equally cute and funny.

@Stotter  
I’m pretty sure this has been done before in the show.

I have to resist.. the petting. Can’t.. move.. away..

Yeah, this one was a bit much. Ranks right up there with the poison joke episode’s floppy horn.

@SeraphimDawn  
However Discord wants them to.

Unicorn horns. HOW DO THEY WORK!?

l-lewd

@Stotter  
Hehehe. X)

@Pagan  

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your current filter.

Since that many months ago. That’s probably hilarious in hindsight now, huh?

i ship them

Well you see young one when a draconequus and a pony love each other very much.