Sonic rainboom (event)

A sonic rainboom is an aerial stunt/event that occurs when a Pegasus pony breaks the sound barrier. Rainbow Dash is the only pony known to have performed the stunt. "Sonic rainboom" is a portmanteau of "sonic boom" and "rainbow." This event appears in the episodes Sonic Rainboom, The Cutie Mark Chronicles, and A Canterlot Wedding - Part 2. It is characterized by a vibrantly-colored ring that expands from the point of the sonic rainboom's occurrence accompanied by a shockwave and a rainbow wake trailing behind the performer of the stunt.

Sonic Rainboom
Sonic rainbooms are first mentioned in the titular episode, where Dash practices her routine for the Best Young Flyer competition. Fluttershy tells her friends that Rainbow Dash is unable to perform the trick despite her dedicated practicing. Later in the episode, Dash performs a sonic rainboom as she speeds downwards to save Rarity and three Wonderbolts who are plummeting down to Earth. The sonic rainboom impresses the competition's spectators and Rainbow Dash manages to save Rarity and the Wonderbolts while also winning the competition. This event is mentioned by Spitfire in the episode The Best Night Ever.

The Cutie Mark Chronicles
The second time sonic rainbooms are mentioned is in The Cutie Mark Chronicles. Rainbow Dash, in a flashback, races against two other Pegasus ponies, and unwittingly performs a sonic rainboom while she speeds along the race's obstacle course. She earns her cutie mark almost immediately afterwards. Both this sonic rainboom and the one in Sonic Rainboomare performed when Rainbow Dash is leading with both front legs forward, while in her failed practice attempts she is leading with a single leg.

The very same sonic rainboom that earned Dash her cutie mark was involved in the other leading characters earning theirs. Applejack, who was visiting relatives in Manehattan, sees its rainbow wake which seemed to point back to Ponyville, and discovers she wants to work on her family's farm. Fluttershy calms animals that have been frightened by the sonic rainboom, and discovers her affinity to animals. Rarity witnesses a giant rock getting cracked open by the sonic rainboom, and discovers it contains gems. She affirms her love for fashion and gems and gets her cutie mark. Twilight Sparkle is personally affected by the sonic rainboom; it takes place during her entrance exam for Celestia's School for Gifted Unicorns, and sends her into a powerful magical state which allows her to hatch Spike. After a few accidents and Princess Celestia's intervention, Twilight discovers her cutie mark. Pinkie Pie draws inspiration from the sonic rainboom's rainbow wake and holds her very first party, which earns her her cutie mark. Pinkie Pie mentions in Sonic Rainboom that she has never seen a sonic rainboom before in her life. This contradicts her flashback in the episode where she witnesses one, however she only realizes what it actually is at the end of the episode.

A Canterlot Wedding - Part 1 and Part 2
The sonic rainboom is featured again in the season 2 finale, A Canterlot Wedding. Rainbow Dash is instructed by Princess Celestia to perform a sonic rainboom for the wedding of Shining Armor and Princess Cadance; later in Part 1, she mentions having been busy preparing for it. She performs the maneuver in Part 2 right as the couple kisses at the end of the ceremony as instructed, and seems to do so very quickly and effortlessly.

Reuse of animation in commercials
In Equestria Girls, clips from Sonic Rainboom and The Cutie Mark Chronicles of Rainbow Dash performing sonic rainbooms are played while Pinkie Pie sings about "seeing rainbooms."

In There's a Pony For That, clips from Sonic Rainboom of Rainbow Dash performing a sonic rainboom are played.

In the Saturday Girls Block promo, clips from Sonic Rainboom of Rainbow Dash performing a sonic rainboom are played.

In a bumper set just after Rainbow Dash completes her sonic rainboom in A Canterlot Wedding - Part 2, she is shown performing another sonic rainboom in front of Tori Spelling.

Similar effects
The "rainbow colored shockwave ring" effect is used again in different episodes. When the ponies use the Elements of Harmony to defeat Discord in The Return of Harmony Part 2, a similar ring emanates from them when they activate the Elements' magic. In Lesson Zero, Rainbow Dash demolishes a broken-down barn for Applejack in by flying into it. Dash crashes into the barn, creating a colorful mushroom cloud and a ring-shaped shockwave much like that of the sonic rainboom. The sound effect is also re-used for the shockwave which removes the changelings from Canterlot, Discord's defeat, and philomena's regeneration and related 'Magic' sounds associated with the sonic rainboom are also used in other places.

In other media
In the My Little Pony Live Show, Rainbow Dash describes her plan to impress the Wonderbolts at the Grand Galloping Gala. The plan is similar to the one she describes in The Ticket Master, but its grand finale is the sonic rainboom rather than the buccaneer blaze.

A sonic rainboom is involved in The Magic of Friendship, a story stated to take place when Twilight Sparkle and Spike are new to Ponyville. In the story, Rainbow Dash performs a sonic rainboom in the process of saving Applejack from being hit by barrels. Pinkie Pie reacts to this by shouting "Wow! A sonic rainboom!" while jumping up and down.

The objective of Rainbow Dash's Rainboom Game is for Rainbow Dash to create a sonic rainboom to decorate the sky (specified in the original version to be after the wedding ceremony of Princess Cadance and Shining Armor), as she does in A Canterlot Wedding - Part 2.