"Badger Badger Badger" is a Flash animation made in 2003 by Weebl, the owner of the site weebls-stuff.com. The animation is hosted on its own site, called badgerbadgerbadger.com. It was also uploaded to Newgrounds, a Flash animation sharing site, in 2003. In 2008, Weebl posted a minute-or-so-long clip of the animation to YouTube, where it has since garnered over 26 million views.
The animation begins by showing a green field and a single badger with its arms out and its knees bent. The singer starts singing in monotone the word "badger" over and over. On each repetition of the word "badger," a new badger appears from nothing, and all pre-existing badgers flex their knees and wave their arms.
After three measures of "badger," the scene changes, showing a red and white-dotted toadstool, and the singer says, with feeling, "mushroom, mushroom!" The badger scene and the toadstool scene repeat twice. After the fourth instance of the badger scene, the viewer is jarred by a screen of vibrant red and yellow, featuring an explosion-esque shape with the word "ARGH!" at the center. This is reminiscent of the exuberant onomatopoeiae of Golden Age comic books.
Then the scene changes to a stereotypical desert, complete with a cactus, with a green snake slithering from left to right. The singer wails, "A snake, a snake! Snaaake! Oh, it's a snaaake," in a despairing tone. This is the only part of the song that features harmony.
After this, the sequence repeats--badger scene, mushroom scene, etc.--with the next snake scene happening after the fifth repetition of the badger scene, instead of the fourth.
"Badger Badger Badger" appealed to the sense of humor of the mid-aughts internet, and quickly became a meme, spawning parodies, remixes, and real-life recreations. A sample of some more notable remakes may be seen on Know Your Meme.
Edited to add a description upon request (thanks, Silverai_me!)
"Badgers : animated music video : MrWeebl." YouTube, uploaded by Weebl's Stuff, 28 Jun. 2008, youtube.com/watch?v=EIyixC9NsLI. Accessed 25 Aug. 2019.
Multiple authors. "Badger Badger Badger." Know Your Meme, 20 Jun. 2009, knowyourmeme.com/memes/badger-badger-badger. Accessed 25 Aug. 2019.
TheWeebl. "badger ver.1." Newgrounds, 1 Sep. 2003, newgrounds.com/portal/view/120321. Accessed 27 Aug. 2019.
Weebl. Badger Badger Badger. 2003, badgerbadgerbadger.com. Accessed 25 Aug. 2019.