SpongeBob: Re-Hydrated is a CGI-animated SpongeBob SquarePants short that was aired in 2003. It was made in the style of a teaser trailer, and features SpongeBob dressed as Neo from The Matrix film franchise fighting an army of Patrick Star clones dressed as Agent Smith.
The exact nature of the short was unknown for a long while, with people speculating it to be a game cutscene, a commercial, a fan-animation, or even a full SpongeBob episode. However, in 2017 it was clarified that the footage previously found was actually the entire short, minus the original audio.
Attention was first brought to the short in early 2016 after a few seconds of footage were discovered in a Nicktoons channel bumper from 2003. A thread was made on 4chan's /co/ board in an attempt to find more information on it, and one anonymous user claimed it to be a 10-minute short called The Spongetrix that was included on a Jimmy Neutron VHS. This was quickly debunked as a hoax, but regardless, the rumor and fake title persisted for quite some time.
After, the search spread to sites such as the Lost Media Wiki and SpongeBuddy Mania. In April of that year, 30 seconds of footage were found in the 2013 portfolio of a Nick Digital animator named Goopy Rossi. This revealed the true title of the short as Spongebob: Re-Hydrated, and also confirmed the connection with The Matrix Reloaded.
The search continued for a few more months, but began to stall later that year due to a lack of any solid leads. However, on April 15, 2017, a YouTube user named Vailskibum94 created a video on the topic. Despite containing a good deal of outdated information and inaccuracies, the video revived interest in the short, and later that day users on the wiki Encyclopedia SpongeBobia were able to contact animator Randy Gossman. He posted a public message to the wiki to clarify these rumors.
Gossman stated the short was nothing more than an extra made by the animation team of the game Employee of the Month, which may have aired on Nicktoons in the network's early days. The short was made without involvement from the writers of the main series, and reused 3D models from the game Operation Krabby Patty. Most importantly, though, he stated that no more footage exists than the 30 seconds that were already discovered.
Though the entirety of the video footage is now confirmed to be found, Gossman also claimed that short originally had a different audio track with sound effects. This would make sense as the audio on the currently-found footage is a generic track that plays throughout Goopy Rossi's entire demo reel, not just the footage. This audio has yet to be found.