My Little Pony: Friendship Is Magic - S01E10 - Swarm Of The Century

In the "My Little Pony: Friendship Is Magic" episode "Swarm Of The Century", Fluttershy brings back to Ponyville a seemingly harmless creature called a Parasprite, which turns out to become a problem, as soon as it starts to multiply.

When the ponies managed to drive all of the Parasprites back into the Everfree Forest, they return to Fluttershy's cottage, only to find it swarming with more Parasprites, just because Fluttershy couldn't stop herself from keeping "just one". When Twilight Sparkle realises that they can't round up all of the Parasprites, Rainbow Dash suggest that they "call in the weather patrol", after which she flies up into the air, and prepares to create a tornado, to catch all of the Parasprites in one sweep. Before she makes the tornado, Rainbow Dash puts on her flying goggles, and proclaims that it's "Time to take out the adorable trash!", after which she flies in, yelling like a warrior going into battle, and beating her chest.

(Between you and me, this was the absolutely first scene I ever saw from "My Little Pony: Friendship Is Magic", and it shaped my whole perception of the character of Rainbow Dash. It actually took me a while to grasp the fact that she was a girl. I truly believed that she was a boy. But she turned out to be a tomboy, instead. Believe me, I wasn't at all disappointed when I found out that she was a girl. In fact, it filled me with joy when I realised that she was an extreme tomboy. I'm actually still waiting for her to do some chest beating in the "My Little Pony: Equestria Girls" series. Hehe.)