Boy Bullies

Three pegasus stallion jocks known as Dumb-Bell, Hoops, and Score, or known together as the Boy Bullies, referenced from page 35 of Little Brown's My Little Pony: Elements of Harmony reference guide, were a couple of ponies that picked on Rainbow Dash and Fluttershy back in Junior Flight Camp, whom they called "Rainbow Crash" and "Klutershy". Hoops, "Dumb-Bell", and "Score" first appear in Sonic Rainboom, and only Hoops and "Dumb-Bell" appear in flashbacks during The Cutie Mark Chronicles. "Score" is the only one out of the three without any dialogue. The three bullies also appear on the and the  posters.

Junior Flight Camp
Hoops and "Dumb-Bell" appear in The Cutie Mark Chronicles on Fluttershy's and Rainbow Dash's flashbacks. On Fluttershy's flashback, after she attempts to fly but fails, the two young colts start to harass Fluttershy of not being able to fly, only to be stood up to by Rainbow Dash (or Rainbow Crash as they called her). Rainbow decides to challenge the two bullies in a race, but while racing, "Dumb-Bell" crashes into a column and Hoops gets spun out, and right after, Rainbow Dash preforms a Sonic Rainboom and earns her cutie mark.

Young Flyers Competition
When Hoops and "Dumb-Bell" grew up, they ended up working at the Clousdale Cloud Factory. As Rainbow Dash and Fluttershy returns to Cloudsdale for the Best Young Flyers Competition, Hoops, "Dumb-Bell", and "Score" meet up with them as they arrive and start teasing Rainbow on how she got kicked out of Flight School, and how she doesn't have a chance on winning the competition, and how the Sonic Rainboom is an old mare's tale, which really brings Rainbow down. A short time after Rainbow's friends arrived to Clousdale and were touring the Cloud Factory, the three stallions were admiring Rarity's new wings that were made by Twilight Sparkle. After they witness Rainbow Dash winning the competition, and after saving the Wonderbolts and Rarity, they start to gain respect for Rainbow, and apologize to her for giving her a hard time, and they ask Rainbow if she can hang out with them, but Rainbow rejects their offer to hang out with the Wonderbolts.

Other depictions
TBA

Quotes
"It's our old friend Rainbow Crash!"

- Hoops, Sonic Rainboom

"Get kicked outta any flight schools lately?"

- Dumb-Bell, Sonic Rainboom

"Face it, Rainbow Crash. Flight school had too many rules, and not enough naptimes for you."

- Dumb-Bell, Sonic Rainboom

"Nice going, "Klutzershy"! They outta ground you permanently."

- Dumb-Bell, The Cutie Mark Chronicles

"HA! My baby brother can fly better than you!"

- Hoops, The Cutie Mark Chronicles