This is easily one of the very best episodes of the first season of My Little Pony: Friendship is Magic. I give you, "Sonic Rainboom"!
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Basically, Rainbow Dash (the cute little tomboy pegasus) is entering the Young Flyers competition. Once before she pulled off a previously believed impossibly move, the Sonic Rainboom, and she has been trying to live back up to it ever since. She has been practicing like a demon for the contest (rare for her; Dash is the "naturally gifted but lazy" type, and usually gets by on talent rather than skill). However, her confidence is getting a bit shaky, and so she asks her friends to give her some moral support. Twilight Sparkle attempts this by using her magic to give Rarity (the little white unicorn) wings. But they start going to Rarity's head, and Dashy gets only more frightened until... well, you'll have to see the show.
I like this one for delving into the character's personalities a little more than you'd expect from a "kid's show". Dash is usually depicted as brash, fearless, and even arrogant, but here we see her as being genuinely scared that she doesn't have what it takes and that her previous pulling off a "Sonic Rainboom" was due to her being a one trick pony. Indeed, more than one she looks downright vulnerable, which is rare for her. It's odd to feel protective for Rainbow Dash.
And of course "Drag Queen" Rarity. Admittedly, she went a little over the top, but Rarity is a little vain. And the adulation of the masses in Cloudsdale didn't help. Then again, alicorns are so rare they are seen as literal gods in the setting, so some of it was justified in setting. And while Rarity was an awful showoff, you'll notice that she was quite subdued afterwards -- and that unlike everyone else she didn't walk on clouds. Everyone else had that cloudwalking spell, but not her. A rare bit of continuity for a "children's' cartoon"!
And lastly and most humorously, we see Dashy flying off with the two male Wonderbolts proudly saying that "I've got plans!" Given her 'Rainbow Slash' reputation -- really, the poor filly has become Ponyville's public bus in fanfic (you know, she gives everyone a ride) -- one wonders if this wasn't a joke on the part of the animators.
Best all!