During Twilight, Fluttershy, and Pinkie Pie’s pursuit of finding their friends, the Cutie Mark Crusaders were making their attempts in fixing the whole age mess that Discord caused in Equestria. Their best bet was to go and see Zecora, so they embarked to the Everfree Forest in the hopes of meeting with her. To their surprise, the forest still remained in tact, most of it at least.
 
Apple Bloom: C’mon crusaders. We’re almost there, I think.  
Scootaloo: You said that five minutes ago.  
Sweetie Belle: carrying Cheerilee I just hope that Zecora isn’t a small foal either, or we’ll have to look after two babies.  
Apple Bloom: Look girls! sees Zecora’s home in sight  
Scootaloo: Finally, we’re here.  
Apple Bloom: runs to the door and knocks Zecora, are you there? knocks again Zecora?
 
The door opens and the crusaders are about to greet their friend, but instead somepony else answers. The pony that greets them is a green pony with a somewhat familiar hair style and bonnet.
 
???: Hello there.  
Apple Bloom: Um… Hi, I was wonderin’ if Zecora happens to be home right now.  
???: You mean that nice lil’ Zebra friend? She’s home alright.  
Sweetie Belle: Did you say little?  
???: Sure did. Why don’t y’all come and make yourselves at home.  
Scootaloo: Thanks.  
???: Aww, what a cute foal ya got there. Is she your lil’ sister or somethin’?  
Sweetie Belle: Uh… yeah. Her name’s Cheerilee. Say hi Cheerilee.  
Cheerilee: looks at the mysterious green pony Baba.  
Sweetie Belle: She’s still too young to start talking yet.  
???: Hi to you too lil’ filly.
 
The ponies go inside and notice a young foal playing with an all too familiar doll. Also, they saw their friend Zecora, but noticed that she too had undergone a change in age much like the mane six.
 
Zecora: Hello there fellow fillies, what brings you to my ocassion of festivities?  
Apple Bloom: Zecora? Is that really you?  
Zecora: Indeed, there is no other one but me? And who may I ask is the name of thee?  
Apple Bloom: It’s me Apple Bloom!  
Sweetie Belle: And I’m Sweetie Belle.  
Cheerilee: crying  
Sweetie Belle: Oh no! Don’t cry Cheerilee.  
Scootaloo: I’m Scootaloo. walks over to the cauldron with Zecora  
Apple Bloom: Ya don’t remember us at all?  
Zecora: I’m afraid not. Forgive me for not being the hope that you saught.
 
Apple Bloom walks away with disappointment and decides to talk with the mysterious green pony who is tending to the foal beside her.
 
???: Doin’ alright?  
Apple Bloom: sigh No.  
???: Sorry to hear that.  
Apple Bloom: … How did you two come across Zecora?  
???: Well, this lil’ colt and I were at this farm all by ourselves while a bunch crazy stuff was goin’ about. This lil’ guy was chewing away at this here doll. I couldn’t leave him, so I took him with me to see if I can find help. We got lost in the forest for a while, but then Zecora found us and let the two of us take refuge.  
Apple Bloom: Wait a sec, you said a farm. Did that farm have a lot of apple trees?  
???: That’s right.  
Apple Bloom: And this lil’ foal here was at the farm too?takes a closer look  
???: Yup.  
????(red foal): chewing on the doll  
Apple Bloom: It can’t be! notices who the foal resembles Big Macintosh!?  
Big Macintosh: still chewing  
Apple Bloom: Then that means looks back at the green pony GRANNY!  
Granny Smith: What!? Are you blind or somethin’? I’m no granny.  
Apple Bloom: heads back to Zecora We’ve gotta make some kind of potion or what not that’ll turn everypony back.  
Scootaloo: But how, I don’t think Zecora even remembers that stuff.  
Apple Bloom: Hey Zecora, do you know anything about making an age potion?  
Zecora: I can’t say that I do, but how about instead I whip up a nice and tasty stew?  
Scootaloo: I guess we’re on our own then.  
Apple Bloom: Looks like we’ll have to make our own potion then.  
Sweetie Belle: Uh, a little help you two. trying to calm a crying Cheerilee
 
With greater problems against them, the crusaders are on their own in creating a potion that will help remedy everypony’s predicament.

This really needs to be a thing. o.o

Headcanon on pic:
 
It is well and likely Granny Smith’s birthday, and for her day, the CMC wanted to make a youth potion for her, enlisting the help of Zecora to do so. While the potion’s a-brewing and the CMC are out back gathering ingredients, they all spy Cheerilee and Big Mac, together, taking Granny to the hut as well. Seems they’d had a similar idea.
 
Of course, some unfortunate mishap makes things explode. By the time the smoke clears and the CMC rush back inside, all the inhabitants have been significantly reduced in age. Zecora says she can turn them back to normal, but she notes that in her youth, she was a precocious little scamp. Add that on top of Baby Mac and Cheerilee, and the CMC have got their hooves full.

Granny Smith ought to be OK with this. 2 full lives!

Wait a minute…
 
Mac and Cheerilee became babies, Granny Smith is about the CMC’s age (possibly a touch older) so.
 
How old is Zecora‽

So, who wants to try the potion next?

@Flammie  
it means that they “Regressed” in “Age” becoming “Younger” than what they were originally.

MAKE THIS AN EPISODE RIGHT NOW!!!

whats with young granny smith and young zakorra

I guess in this scenario Granny Smith may be the wisest of them all… Many years of wisdom, now in a less senile form.
 
Though, eccentrism shall abound.

I somehow get the feeling Discord is behind this.

i’ll foal sit big macintosh if you want me to….

I don’t like the look in Zecora’s eyes. It screams “AHAHA! I HAVE NO IDEA!” in response to the question “DOCTOR! ARE YOU SURE THIS WILL WORK?”

It means growing younger.

No seriously, what does Age Regression mean?

Reminds me of Dexter’s Lab.

YEAH!!! AGE REGRESSION!!!…  
Wait, whats age regression?

Seems to be the new pony meme is age regression. ^. :-/