Double Rainboom is the name of a My Little Pony: Friendship is Magic fan film written, produced, and directed by Zachary Rich, better known by his deviantART name, FlamingoRich, formerly known as Flamingo1986. It is created to be his first senior film as per requirements to graduate from the Savannah College of Art and Design. Its main claim to fame is that it is the first fan-made episode that features "a full orchestral score, studio-quality sound effects, professional voice acting, and 100% show-accurate animation."The plot goes as follows: Twilight Sparkle is developing a potion that would give a major increase to any pony's special talent. Rainbow Dash, being who she is, drinks the highly experimental potion despite Twilight's warnings. And from there on she goes and causes havoc for Ponyville and herself.The official website can be found here.The entire episode was released on March 30th, 2013. It was originally scheduled for Fall 2012, but was ended up being pushed forward for quality reasons. It can be found on FlamingoRich's YouTube channel here.On its release, the episode was promptly met with controversy and debate; while some members of the fanbase found its storyline and crossover elements entertaining, many others were left thoroughly disappointed and deflated due specifically to those very same elements.Double Rainboom lost to Snowdrop on the "Top Ten Pony Videos of March 2013" list.
Also Sprach Zarathustra: Variations of the famous intro are played twice: first when Rainbow Dash is preparing to do her do her double rainboom IN SPACE, then again when Pinkie Pie explains being able to see through the fabric of time and space.
Amplifier Artifact: The potion Twilight was working on seems to be this. It enhances a pony's special talent to ludicrous extremes, allowing them to pull off feats they normally couldn't. Needless to say, Rainbow Dash can't resist giving it a try, and it ends up increasing her speed and durably to where she smashes through the ceiling of Twi's tree home on accident after she tries it out, flies around the town at incredible speeds even for her, allows her to fly into low orbit, and gives her the strength to pull off the eponymous double rainboom that proceeds to tear open a worm hole to another universe. Granted, it does have the nasty side effect of temporarily taking away a ponies natural abilities after it starts to wear off, but it's still manages to be this trope Up to Eleven. Considering what happens later in the animation, it's possible that said potion is actually an unstable form of Chemical-X.
An Aesop: Rainbow Dash learns that she shouldn't take things that don't belong to her. She even writes a letter to Princess Celestia.
Creator Cameo: Zachary Rich's pony avatar appears in the background a few times (and in the beginning of the end credits sequence); he can be seen taking a bath when his roof is blown off by the rainboom, and his outfit appears in Twilight's Imagine Spot for Rarity. The Flamingo Rich logo can also be seen while Ponyville is being destroyed.
Crossover: Rainbow Dash winds up in Townsville and gets chased by 3 certain little girls. If you actually watch the video on YouTube it should come up as more surprising, seeing as the beginning of the video only credits The Hub and FiM and the additional credits to Cartoon Network and Time Warner don't show up until halfway through the video. The disclaimer on the bottom of the page of the official website pretty much gives it away.
Crossover Punchline: At the end of the video, where Rainbow Dash is writing her letter to Princess Celestia about why you should not take things that don't belong to you, Pinkie Pie asks "What will I do with this then?", pulling out Bloo from hammerspace. The Foster's theme tune then plays as the video fades to the ending credits.
Demoted to Extra: Twilight Sparkle, Pinkie Pie, and Rainbow Dash are the only Mane Six members who get any prominence. This wouldn't be a problem if it weren't for the Spotlight-Stealing Squad issue, discussed below.
Foreshadowing: There's a lot of PPGShout Outs, especially when Twilight explains/speculates what effects her potion would have on her friends and herself. Now where does Rainbow Dash wind up after her Double Rainboom stunt?
Genre Blind: Twilight scolds herself for not realizing there's no way Rainbow Dash would be able to resist drinking her potion.
Genre Savvy: But she was also savvy enough to realize that giving Pinkie Pie the potion would enhance her Reality Warping abilities.
Gone Horribly Right: The potion works exactly as Twilight predicted, but it causes Rainbow Dash to become so powerful, she accidentally destroys Ponyville through her carelessness.
Interface Spoiler: Reading the legal disclaimer in the video's description should give you a very large hint about the crossover section.
Meta Guy: The potion gives Pinkie Pie this ability.
Milking the Giant Cow: Several of the characters have difficulty sitting still. With RD and The Powerpuff Girls it's in character, but Twilight definitely has a tendency to make exaggerated gestures with little provocation.
Ocular Gushers: Rarity of all ponies. (BTW Rarity, you may want to let go of Sweetie Belle...)
Pinball Gag: One of the many in a series of creative gags.
Plot Hole: Technically, Pinkie Pie's special talent isn't bending reality, but rather making other ponies happy. Taking this into consideration, Twilight's potion probably shouldn't have worked the way it did.
Power Degeneration: A side-effect of the potion on Rainbow Dash is her loss of the ability to fly after heavy use. Pinkie Pie did not seem to suffer any adverse affects, probably because she used her powers responsibly.
If one paused or even looked quick enough before Rainbow Dash crash lands to the ground during the chase scene, the Stark Enterprises building can be seen in the background of Townsville.
After Rainbow Dash and Pinkie Pie escape back to their own world, in the final shot of Townsville, there are street signs in the background behind Blossom, Bubbles and Buttercup that read "Faust" and "McCracken".
A Companion Cube can be spotted in front of twilight after rainbow dash escapes through the roof of her lab.
As well as some Chemical X, This could explain why Rainbow Dash went to Townsville
BMO can be seen twice. The first is broken in the dumpster where Bubbles drops Talking Dog, and the second is displayed on the front of the "Toy Box" during the chase scene.
The Pizza Planet delivery truck appears in the background during the scene where the Powerpuff Girls meet Rainbow Dash.
The address 221 can be seen on a door right before Rainbow lands in Townsville.
Spike's letter to Rarity that can be seen on the floor next to Twilight is a word-for-word rendition of (the beginning of) Sonnet #43.
Spotlight-Stealing Squad: Another common complaint is that so much time is spent showing off the fandom's favorite background ponies that the Mane Six are shafted. And of course there's the Powerpuff Girls.
There Was a Door: Was smashing through the ceiling really necessary, Rainbow Dash?
Title Drop: "With this power, I can do anything! I could easily do a Sonic Rainboom! Even a... Double Rainboom!"
Villains Want Mercy: The monster surrenders before Rainbow Dash makes the finishing blow. When she makes the monster apologize, he gets down on his knees and cries, promising never to do it again. The Powerpuff Girls still beat him up, anyway.
Walking Spoiler: In case you couldn't tell from looking at this page, there's a big one, in the form of the crossover parts.