"Over 9000" is a popular catchphrase based on an awkwardly translated quote from the Japanese manga anime series Dragon Ball Z that is typically used as an innumerable quantifier to describe a large number of something like "several", "lots", "butt loads" and even the metric "ass tonne".
The line was originally said by Vegeta, one of the main recurring characters featured in the series, and voiced by English voice actor Brian Drummond in the 21st episode of Dragon Ball Z (Saiyan Saga) titled "The Return of Goku," which originally aired on April 19th, 1997. In the English-dub of the episode, the main protagonist character Goku returns to the Earth after intense training in the Other World to square off against Saiyan warriors Vegeta and Nappa. As Goku powers up in rage after learning they had killed his friend Piccolo right before his arrival, Vegeta senses an explosive increase in his power level through his scouter device and yells: "It's over nine thousand!" The scene from the episode was uploaded by 4chan user and YouTuber Kajetokun on October 17th, 2006.
The Power Level
In the Dragon Ball franchise, the Power Level is a recurring concept which denotes the combat strength of a warrior. According to Dragonball Wikia,  the highest number ever officially read aloud from a scouter is Captain Ginyu's reading of Goku's power level, which after powering up, is 180,000. The highest power level ever mentioned in Dragon Ball Z is Frieza's power level of 530,000, said by Frieza himself while battling Nail. According to the Japanese manga publisher V-Jump, the overall highest power level is 2,500,000,000 of Super Saiyan Gogeta.
It is interesting to note that Goku's power level is actually read as "over 8000" in the original Japanese and English-translated mangas as well as the original Japanese anime series.
According to Kajetokun, the video was originally shared with his friends as an inside joke, but it was posted to 4chan's /b/ (random) board by his friend Patrick shortly thereafter. In the following weeks of October 2006, YouTuber Kajetokun's video quickly drew attention from the fans of Dragon Ball, inspiring a series of remix videos on YouTube, various image macros and demotivational posters on 4chan, as well as parody sites dedicated to the phrase on YTMND. The first Urban Dictionary entry for "over 9000" was submitted on November 21st, 2006, defined as:
What the scouter says about Goku's power level. Over Nine thousand
"Vegeta, what does the scouter say about his power?"
"It's over NINE THOUSAAAAAAAND!" (Over 9000)
"WHAT?! NINE THOUSAND?!
The phrase continued to take hold on YTMND and 4chan, where the number 9000 soon became adapted as a slang term to describe something or someone of impressive strength. The meme's notoriety reached its first peak in 2007, when 4chan moderators implemented a word filter that would turn any mentions of the number 7 into "over 9000." In addition to its conversational usage, the original scene from Dragon Ball Z has been also revamped into a four-pane exploitable comic:
In April 2008, Kajetokun was interviewed by Cybernetic Tigerz of Japanator, in which he explained that he had not expected the video to become so popular and that he had originally edited it as an inside joke for his friends.
J: When you made the Dragon Ball cutup, did you have any idea it would go on to become such a huge phenomenon over the Internet? Or was it just something that you made for a small group of friends?
K: I had no idea it was going to get this big. Really it was just a small little something I made as an inside joke for my friends. My friend Patrick posted it on /b/ and then I ended up having like 20,000 views the next day.Then Scott from VGcats front page linked my video and I woke up to 200,000 views.
4chan Trolls Oprah
The phrase "over 9000" once again resurged in September 2008, when an anonymous troll left an alarming message on the official message board of American journalist and businesswoman Oprah Winfrey's talk show, in which he claimed to represent an organized network of over "9,000 pedophiles." Oprah took the bait and read the post before her audience in an episode of the show, which was met by ecstatic responses from the Anonymous community praising the prank as an epic win.
“Let me read you something from our message boards about someone who claims to be from a known pedophile network. It said this. ‘He doesn’t forgive, he doesn’t forget, his group has over 9,000 penises, and they’re all raping children.’ So, I want you to know, they’re organized, and they have systematic ways of hurting children, and they use the Internet to do it.”
A video clip of Oprah's message to her audience was promptly uploaded to YouTube, however it was quickly removed due to a copyright claim by Harpo, Inc. Despite the takedown, numerous remix videos featuring Oprah's mention of "9000 penises" surfaced on YouTube.
Furthermore, overall Google searches for the obscure "Over 9000" DBZ reference also surpassed all searches for the wellknown "HAL9000" from Stanley Kubrick's 1968 science fiction film 2001: A Space Odyssey: