oh so almost like the Futurama episode “Teenage Mutant Leela’s Hurdles”
Twilight is Leela (though she didnt get younger but is only one not getting younger fast)
Granny Smith is Prof Farnsworth (considering she started out old)
Pinkie Pie, Rarity, Fluttershow and Rainbow Dash as Fry, Amy, Bender and Hermes
Technically Spike is Zoidberg (though he got younger but his transformation was different then others)
Twilight is Leela (though she didnt get younger but is only one not getting younger fast)
Granny Smith is Prof Farnsworth (considering she started out old)
Pinkie Pie, Rarity, Fluttershow and Rainbow Dash as Fry, Amy, Bender and Hermes
Technically Spike is Zoidberg (though he got younger but his transformation was different then others)