Given Uncle Grandpa, I’d say this was a 100% intentional crossover. Rather funny, too. From the thumbnail and pointless downvotes, I thought someone had just photoshopped UG into Gummy’s scene.

In case anyone has any doubts and doesn’t want to take the few seconds to search for themselves, from “Pinkie Pride”:  
 
From Uncle Grandpa:  
 
(Nice touch on UG’s shadow, to be honest.)

OH wow I thought I was the only One who thought this.

“Don’t worry, it’s not canon.”

@Joshua  
No, if anybody stole here it’s Uncle Grandpa, though I wouldn’t really call it stealing. It’s probably just a subtle refrence they slipped in that almost nobody would get, and that’s probably that point. I imagine they would have intended it to be a sort of “I RECOGNIZE THAT GAY BLOWJOB” sort of thing for people who watch both and pay attention.
 
Alternatively, it could be entirely coincidental, since like @Blip267 said it is just stock footage.
 
People in animation give each other subtle nods all the time. It’s less stealing and more paying homage to those you respect.

To be fair, this is stock footage.

@I Was Never Here  
So MLP stole from Uncle Grandpa in “Pinkie Pride”?

@Joshua  
Part of the premise of the show is that there are moments, and even entire episodes, where they intentionally seek out the fourth wall and break it then stare at the meta-context that lied behind that wall and wait for it to blink.
 
 
@BillyGGruff  
I think that’s the point. Not trying to defend the show here, but I imagine the implication was very much so intentional.

Just found a new tag for my filter. “Uncle Grandpa”
 
Seriously what kind of backwater hick name is that for a character anyway?

Uncle Grandpa…  

“Good morning!”

Oh great, they’re stealing from MLP now?