@WM-R  
Hi there. You must be new to the internet.
 
But yeah, people overanalyze everything. Especially this show, where somebody once tried to calculate how fast Rainbow Dash was going from the shape of the cone in front of her as she approached Sonic Rainboom. It can be pretty fun to see where you can go with it to be honest. It’s like a fun little exercise in illogic. I had my own go at Pinkie Pie over here >>459151

It appers to be over-analyzing, since those two were throw-away gags. Still, if the fetishis want to use those two parts for base their headcanon, I cannot argue back.
 
 
@Background Pony #E68C  
Because, maybe, when they started to have sexual drives, they found that people wearing diaper (or using them, it depends) were sexually arousing?

@Background Pony #E68C  
Dear diaper fetish haters. Your mothers thaught you to mind your own business (or at least she should’ve), yet here you are, telling people that them liking something you don’t is awful and bad and wrong. What is wrong with YOU?
 
That said, while I love the idea of Pinkie or any other pony is an abdl, I think it was purely for entertainment purposes that they included these gags, and OP is overanalyzing.

Dear Diaper fetishists  
Your mother breaked her back to teach you as a toddler to use the “toilet for grown ups”  
Now approaching twenty (or whatever your current age) you decide to go backwards and wear diapers AGAIN  
WHATS WRONG WITH YOU ?

@WM-R  
Yes, yes they do.

What the hell does ABDL stand for?

I’m…not sure how I feel here. Clearly some thought has gone into this. On the other hand, it’s overanalyzing a show about multi-coloured, magical ponies.
 
This isn’t Star Wars or Gundam, here. Do people overanalyze the Looney Toons too?

@JP  
Judging by the ‘evidence’ provided, I think it means “Adult Baby/Diaper Lover”.
 
Really show professionalism when they don’t even explain what it is they’re talking about.

What’s “ABDL”?

Inflationists had their ride with Spike at your service and MMMystery.
 
I guess other fetishists can grasp at straws too.

Get your twisted fetishes away from my ponies, dammit!

Yeah it’s really reading too much into things. If anything, one of the writers might be into infantilism and that interest seeped its way into the show but even that’s not certain.

Does this qualify for the “diaper fetish” tag?

That sinking, sickening feeling when you stop and realize that a full-grown adult watching a children’s series of cartoons analyzed visual gags to the extent that they felt compelled to write about and categorize a character in a show aimed at children as somebody into infantism.
 
I really can’t get angry at this. I’m just gravely, sincerely disappointed.