Pegasi

Pegasus ponies, or Pegasi, are one of several kinds of ponies that live in Equestria. They are characterized by their wings and their ability to fly, walk on clouds, and control the weather.

Development and nomenclature
Pegasus ponies were introduced shortly after Earth ponies in the original My Little Pony toy line. On the show, they are called either Pegasus ponies or Pegasi, and mostly "Pegasus" for a single pony, though "Pegasus pony" is also used, as specified in the article ponies. Lauren Faust, the show's developer, stated that the Pegasus ponies have a passive kind of magic that allows them to walk on clouds and manipulate the weather.

Pegasus ponies are derived from Greek Mythology, notably the tales surrounding the eponymous flying horse, Pegasus, who was a white horse with wings. Pegasus is also the name of one of the 88 modern constellations.

Origins
The Pegasus tribe was one of the three founding groups of Equestria, as depicted in Hearth's Warming Eve, and its members were responsible with maintaining the weather in return for food that was harvested by the Earth ponies. The pre-Equestrian Pegasus tribe was led by Commander Hurricane, who is played by Rainbow Dash in a historical reenactment. The reenactment depicts the Pegasi as being a militaristic, organized tribe, with an established fighting force and a home in the clouds filled with war-themed monuments. In the reenactment, Commander Hurricane refers to the Pegasi as "a mighty tribe of warriors".

Before the three pony tribes united under the single nation of Equestria, Commander Hurricane intended to name their new home "Pegasopolis" in honor of the Pegasus tribe.

Physical and magical traits
Pegasi demonstrate great speed and agility in the air in multiple episodes. However, in the episode Fall Weather Friends, Rainbow Dash is equally matched on the ground with Applejack, an Earth pony, during an "Iron Pony competition". In the episode Sonic Rainboom, Pegasi naturally walk, sit, and lay on clouds, but unicorns and Earth ponies cannot do so. Twilight Sparkle casts a temporary spell that allows her non-Pegasi friends and herself to walk on clouds. Gilda, a griffon, also stands on clouds in Griffon the Brush Off. In May the Best Pet Win!, several other creatures are shown to be capable of flight perch on clouds. In Putting Your Hoof Down, Fluttershy uses her wings in a similar fashion to hands, using them to get out bits to pay the shopkeepers from her saddlebag.

Pegasus wings are sometimes tremendously strong; athletically-trained Pegasi support most of their body weight on them in Hurricane Fluttershy, Rainbow Falls, and Equestria Games. Scootaloo, who is unable to fly, uses her wings' power to propel her scooter and a wagon carrying Apple Bloom, Sweetie Belle and the occasional third pony, at high speeds and over inclines in the episodes The Cutie Mark Chronicles, One Bad Apple, and Flight to the Finish.

The sonic rainboom is an aerial display that is first featured in the episode Sonic Rainboom. Pinkie Pie describes it thus: "The sonic rainboom is legendary! When a Pegasus like Rainbow Dash gets going sooo fast... BOOM! A sonic boom and a rainbow can happen all at once!" Rainbow Dash performs the sonic rainboom three times in seasons one and two: once as a filly in a flashback in The Cutie Mark Chronicles, once in Sonic Rainboom, and once at the conclusion of A Canterlot Wedding - Part 2.

Weather control
At the first episode of the series, Twilight Sparkle meets Rainbow Dash, who hops on a cloud to make it rain and wash mud off Twilight, and then air-dries her by flying around her. Twilight tells Rainbow Dash she is "supposed to be keeping the sky clear"; Rainbow then clears the skies of clouds (in "10 seconds flat"). In Sonic Rainboom, the main characters visit the Cloudsdale weather factory. They walk through a chamber where Pegasi handcraft snowflakes, an open area where Pegasi mix up rainbows and finally the cloud-making department.

Rainbow Dash creates thunder and lightning by violently punching or bucking clouds in Griffon the Brush Off and Luna Eclipsed, to prank ponies. Princess Luna and Derpy each trigger thunder and lightning the episodes Luna Eclipsed and The Last Roundup, respectively. In Tanks for the Memories, Rainbow Dash visits the weather factory, which holds lightning bolts in jars laid about.

In the episode Winter Wrap Up, Rainbow Dash leads the weather team during the annual Winter Wrap Up. The team, which wears blue vests, consists mainly of Pegasus ponies. In the song that shares its name with the event and episode, the weather team clears the skies of clouds to let the sun warm up the land and melts the snow. Rarity mentions that the team also "guides the birds back north for the spring". On a frozen lake, Twilight Sparkle encounters Pinkie Pie, an Earth pony, who is helping the weather team by acting as a "lake scorer". Pinkie Pie cuts squares in the ice with her ice-skates and explains to Twilight that it helps the rest of the Weather team break the ice layer. Pegasi usher in winter in various activities in Tanks for the Memories, culminating in an accidental snow blast from the Cloudsdale weather factory that covers Ponyville in snow.

At the beginning of the episode Hurricane Fluttershy, Rainbow Dash hosts a mandatory meeting for all Ponyville Pegasi, in which she shows a film that states, "A team of Pegasi combine their wing power to create a jumbo tornado, powerful enough to pull water out of the local reservoir and funnel it all the way up to Cloudsdale." This, Rainbow Dash explains, supplies Cloudsdale and all of Equestria with rainwater. Rainbow Dash also stresses that the ponies' combined power must exceed a minimum of "eight hundred wing power". During training, Twilight Sparkle uses an "anemometer" to gauge wingpower. Rainbow Dash's score on the anemometer was 16.5 wingpower and Fluttershy's post-training score was 2.3 wingpower.

Non-pegasus weather control
Earth ponies and unicorns can play a part in controlling the weather too. Autumn leaves are shed from the trees in a foot-race of all pony kinds in Fall Weather Friends. Pinkie Pie is part of the Winter Wrap Up weather team in the episode of the same name, described in the previous section. Other Earth ponies clear the snow with snow-ploughs, and Spike mentions that in Canterlot, unicorns wrap up winter. When Rarity temporarily gets Rainbow Dash's cutie mark in the episode Magical Mystery Cure, she uses her unicorn magic to arrange the clouds above Ponyville in a checkerboard pattern.

When the ponies venture for the first time into the Everfree Forest, Applejack surmises that "It ain't natural; folks say it don't work the same as Equestria". In Bridle Gossip, Applejack, Fluttershy, and Rainbow Dash elaborate that the plants grow on their own, animals take care of themselves, and clouds move without pony intervention.

Other magical creatures can affect the weather too. Discord has strange effects on all of the surroundings, including making clouds rain chocolate milk in The Return of Harmony Part 1. Windigos, "winter spirits that feed off fighting and hatred", create snow and blizzard: "the more hate the spirit feels, the colder things become," according to Clover the Clever, the historical character that Twilight plays in the Hearth's Warming Eve play.

Residence
Pegasus ponies live in Ponyville, where all three types of ponies live, and Cloudsdale, which is exclusively populated by Pegasus ponies since only they can walk on clouds. Fillydelphia is mentioned in Hurricane Fluttershy to have a Pegasus pony population as well. In the episode It's About Time, Rainbow Dash mentions a town called "Las Pegasus". Canterlot is almost devoid of Pegasus ponies, with the exception of some Pegasus Royal Guards.