Extra Thicc refers to an exploitable scene from the 2001 animated series Samurai Jack, in which the shape-shifting master of darkness Aku, is shown ordering "extra thick" henchman for his plan. Online, the scene is humorously utilized in reference to the slang term "thicc".
In Samurai Jack Season 4 Episode 48 titled "Jack versus Aku," the main antagonist of the series, Aku, is shown picking up a phone and making an order for what seems to be a large pizza, but is actually for a bounty hunter. Nearing the end of his order, Aku is asked a specific detail about the henchman, to which he replies with "Extra thick!" After a a particularly enthusiastic laugh directed towards his order, the phone call abruptly ends (shown below).
While the scene and episode were particularly well-known among and outside the Samurai Jack fandom, the scene did not receive major attention until the coincidental meshing of the phrase "Thicc," alongside the renewal of Samurai Jack. On October 9th, 2016, YouTuber Nepeta Leijon uploaded a remix of the phone call scene (shown below). Within six months, the video gained over 160,000 views and 200 comments.
On March 12th, 2017, YouTuber Ballistic Waffle uploaded a similar remix titled "Extra ＴＨＩＣＣ," which garnered upwards of 650,000 views and 1,000 comments over the next two months (shown below, left). On March 27th, YouTuber Pyrocynical uploaded a video titled "Extra Thicc," which features a music remix of the scene during the opening sequence (shown below, right). Over the next month, the video received more than 700,000 views and 5,900 comments.
On March 28th, Redditor acivilpsycho posted a screenshot of a YouTube video titled "Aku saying 'Extra thick' for 10 hours" along with a photoshopped text message asking to "please disconnect from the Bluetooth speaker" to /r/pyrocynical (shown below, left). On April 1st, Redditor aturnernator posted a picture of the character Pearl from Steven Universe followed by the Extra Thicc Aku image to /r/stevenuniverse (shown below, right).