Crazy Headcanons

Carrot Cake has a brother he doesn’t like talking about named Urinal Cake.
 
He’s one of the only ponies in their family to not go into baking.

The pony life is turned upside down with G5.

Chrysalis and Tirek were born on April 20 and September 11 respectively.

Indigo Zap is actually a much darker color as a pony, hence why she has human coloration in EQG.

Equestria Girls Pinkie becomes chubby after marrying Cheese

Mildly NSFW:
 
Rarity is a prostitute and you can’t change my mind. Look at her, always flirting and so focused on wealth.

@GenericArchangel  
Do you really think she’d be such a poor one as to have to hold down such an expansive day job?

@Latecomer  
It’s a side job for her. She’s also probably one of the classy variety: few clients who pay quite a lot of money. The sort that is termed “escort” more than ”prostitute,“ and definitely not ”whore.“

@GenericArchangel  
Well, I’d agree on that - even in an AU of mine where all the Manes are of said profession, she’s quite insistent with her terminology. (Which AJ, who considers all of them the same about as respectable as the last implies, riles her up over a lot.)

@Latecomer  
Now that is a given, she’d be scandalized if you used any other word for it. She finds it so respectable she even reports it as taxable income- regardless of if it’s legal or not in Equestria, which I suspect it would be.

@GenericArchangel  

 
In the Equestria Girls world, not just Rarity. Pinkie is also secretly a prostitute who offer her services to the male students

Fluttershy is hella M.

Cozy Glow’s plan to drain the magic from Equestria was all part of the real Grogar’s plan. He was stuck in another realm and he needed magic to return to Equestria. Cozy was a creation of Grogar, unknowing that she’s helping him.

In “Guardian” Pharynx was one of the few Changelings from that group to survive, and he still has nightmares about Derpy.

Blueblood and Fleur-de-Lis are siblings.

In the ancient griffon tongue, all proper nouns started with the a fricative G (International Phonetic Alphabet /ɣ/), from an ancient word meaning “person”. In Equestria, some traditional griffon names start with Y (IPA /j/), because in Old Ponish /ɣ/ sometimes palatalized to the semivowel. Other griffons whose ancestors have lived in Equestria for a long time have dropped the G- or Y- naming convention.

There are no humans in Equestria because ponies ate them all.

Pegasi are the weakest major race physically. I think it’s the hollow bones

Unicorns are on average the smartest of the three pony races.

@Goku Black  

 
But also the most prone to mental and emotional disorders.

@Random-Rambling  

 
they have contact with the Warp

@Sufficienttosay
 
All ponies can use magic, but unicorns having their magic so close to their brains is what causes this.

@Dustcan  
As a voraphile,I find that very hot.

Twilight Sparkle was born because Hasbro want a mixture between Optimus Prime (leader and main hero) and Wheeljack (Genius whose plans often backfire) on her.

Whenever Gallus gets angry, he raises the feathers of his neck to look like a sunburst, like roosters do when they fight.