Jimmy Neutron: Boy Genius (partially found TV promos for Nickelodeon animated film; 2001–2002)
When the Jimmy Neutron: Boy Genius movie was being released around 2001, Nickelodeon interrupted some of their shows with little gags to promote the movie. One such gag (supposedly) had the audio track on a Rugrats episode changed, another one giving the SpongeBob cast hair in the style of Jimmy's, and another one that is confirmed to exist had a SpongeBob SquarePants episode being made with puppets. At the moment, no footage exists, due to it coming on at random times. Only one (low quality) picture of the SpongeBob "puppet show" gag currently exists, and is said to be taken from the Season 1 episode, "Hooky".
March 7, 2016 Update: A slew of comments happened! First of all, wiki member CDCB2 has an interruption during the SpongeBob episode "Employee of the Month" that displays Jimmy and Goddard playing fetch with the Nick "network bug". CDCB2 says he'll upload it once he finds the disc.
Next, a lot of sightings have been claimed. An anonymous person claims that during the Rugrats episode "Music", he gave the Rugrats cast his hairstyle much like the SpongeBob one above. Another anonymous person claims that during the Hey Arnold! episode "Helga Sleepwalks", Jimmy replayed a scene of Helga eating pork rinds a few times. Yet another anonymous person claims "Squeaky Boots" getting the "puppet show" treatment, and yet another anonymous person claims that SpongeBob episode "Culture Shock" recieved not one, but two interruptions. The first one was where Squidward talks to the group behind the curtains. The anonymous user says that supposedly, he was given Jimmy's hairstyle. The second one was that the colors supposedly inverted for a few seconds. The same anonymous user claims that during another episode, a part of the episode repeated a few times, much like the "Helga Sleepwalks" situation above.
This has been Nodog, signing out.