Nah, that’s too easy.
 
Try asking them to give the names of all the Mane 6 in under 30 seconds. (I remember that even 10 episodes in, I would always remember 5 of them, then spend the next 20 seconds trying to figure out which one I’ve forgotten this time.)
 
Or even better, you could just ask them to do it in 10 seconds flat and see if they facepalm.

Pony Mcponyson ha!

Princess Luna.

Princess Ponyhead. Ha, there!

Easy, there’s Pie-hater Dash, Mean Rainbow Dash, EQG Rainbow Dash, lots of characters.

Luna don’t talk with your mouth full!

Did she hate Rainbow Dash? She asked me with her name… 🤔

A sampling of names off the top of my head:  
G1: Sweet Stuff, Firefly, Applejack, two different Twilights, Fizzy, Tex, Melody, Lancer, Clover, Rozy, etc.  
G2: Dainty Dove, Clever Clover, etc.  
G3: Minty, Pinkie Pie, Razzaroo, Kimono, Apple Spice, Flitter Flutter, Brights Brightly, Starsong, etc.  
G4: Fluttershy, Big Macintosh, Derpy Hooves, Applejack, Apple Bloom, etc.

Wait, I thought it was called the Rainbow Dash show. Well it should be called the Rainbow Dash show!

Laa-Laa?

Obviously, Communist Starlight

Umm… Twilight… something? Shutterfly. Ponka. And Rawr or something. Plus Rainbow Dash. That’s all of the five main characters.

Jackie Chan.  
Yeah.  
Bet you feel stupid now.