The trope was averted for the very first Nicktoon to hit it big, The Ren & Stimpy Show. Because it came before this trope became prominent, it was only seen on Nickelodeon twice a week (on SNICK and on Sunday mornings). However, it was also run on MTV at the height of its success. Another likely reason it wasn't given marathon airings was the fact that they had so few episodes to run in the first place.
Rugrats was the first show to really get this treatment. After the show was brought back from hiatus, and saved from cancellation at the last minute, due to the ratings for the reruns being high and the show was put back into production, it dominated most of the lineup and was running every day, at least four times a day (though in recent times, this is nothing, compared to how SpongeBob is treated). This led to Nickelodeon using Klasky-Csupo (the studio behind Rugrats) to produce at least six new shows for the network, including the RugratsSpin-OffAll Grown Up! which was born from another over-hyped special that got Nickelodeon's highest ratings ever at almost twelve million viewers. Meanwhile, all the other Nicktoons were basically ignored or cancelled outright. Though Rugrats was nowhere near as Adored by the Network back then as SpongeBob is now.
SpongeBob SquarePants could be the posterchild for the trope. The show runs at least eight times on an average weekday. It will often be the first thing they show in the morning and the last thing they show at night, before turning into Nick At Nite, and it's the only show that they run at all different hours of the day to get pre-schoolers, after-school kids, and evening teenager audiences. "Special" SpongeBob episodes are hyped up and promoted more often than the regular Nicktoons on the network. Some days, it gets more airtime than all the other Nicktoons still on Nickelodeon combined. During 2009-2011, repeats get higher ratings than the average that most kids' shows nowadays have. Go on TV By The Numbers, look at the top cable ratings for the weeks and check out how many episodes will be there. However, ratings for the show have lately dropped, probably due to daily overexposure.
There was a three-day long marathon of nothing but SpongeBob in 2009 to promote the 10-year anniversary and the T or S special. Later during that week, even Nick At Nite aired a special about the production of the show.
On 7/18/10, an unannounced twelve hour marathon of SpongeBob plagued the channel, before an airing of Adventures In Babysitting.
On 7/29/10, of the 11 hours of Nickelodeon not including Nick At Nite and Nick Jr, nine hours were filled with SpongeBob and iCarly alone without any of their current Nicktoons showing and only two other shows aired.
During 2010, the Australian Nickelodeon had SpongeBob running from 12AM-6AM every night, for over a year.
A schedule change in April 2011 resulted in SpongeBob having over 60 airings that week.
The UK Nickelodeon had 502 hour marathon of Spongebob in Summer 2011, for the Clash of the Bottom competition, where kids had to vote for their favourite main character. To top that off, it was the second-longest TV show marathon of all time, only being beaten by Boomerang UK's Scooby Summer.
On July 21, 2012 Nick aired a Spongebob marathon to promote the "Super-Spongey Square Games", an hourlong block of new episodes devoted to sports. They also aired the 1-hour special "Truth or Square" and the movie.
Whenever a new episode is going to be aired (and a 15-minute one at that), Nickelodeon will hype it up with a big marathon and tons of promos. That there just shows how much that Nickelodeon absolutely loves SpongeBob.
Hollywood news website Deadline reported that in January 2012, SpongeBob filled up about a quarter of Nickelodeon's schedule. As of October 2013, the Sponge now accounts for roughly 45% of the network's airtime!
iCarly spent several years as the adored live action show counter-part to Spongebob. Not surprisingly however, as it was the only show to even come close to matching Spongebob's ratings and popularity, up to and including an episode that broke the 12 million viewers mark. Like Spongebob it got the marathon treatment regularly.
Dora the Explorer is the second most run cartoon on Nickelodeon, airing at least four times during the morning hours.
Sometimes Nick combines overplayed shows into giant marathons or blocks that can take up entire days:
On 11/26/10, they played a six-hour SpongeBob marathon, followed by an iCarly marathon at 3, ending with iStart a Fan War at 7, and wrapped it up with the premiere of the Victorious special, "Freak the Freak Out".
On Latin America's channel, almost all weekends are 48 hour marathons of either SpongeBob or iCarly.
As of May 18, 2012, Nickelodeon can now be called "The Spongebob and Kung Fu Panda: Legends of Awesomeness Network". Why is this? Because Kung Fu Panda plays for 2 1/2 hours on weekdays, making it the second-most run show on Nick.
Fanboy and Chum Chum: Massive blocks on both Nickelodeon and Nicktoons, It seemed for a while that you couldn't go a single day of the week without seeing at least three episodes of it.
Often the same three episodes. Again and again and again. Seriously, for a while you could only see three to five episodes, total, of Penguins Of Madagascar and Fanboy and Chum Chum, even with the knowledge that other episodes probably existed. They would play them in hour blocks, yet you never seemed to catch a new episode.
T.U.F.F Puppy has been getting adoration in the same way as Fanboy and Chum Chum, a new show that is being shoved down our throats, when SpongeBob has the day off.
Dragon Ball Z Kai is shown multiple times every day with flimsy excuses for marathons. It's 11/11/11? They promise to show 11 hours of the show. It runs at least 4 episodes a day.
The block-series, Nick Studio 10, was crammed into the program during any possible rerun. It got so bad that Nick actually interrupted whatever show is playing to air a random clip of something and/or a Studio 10 skit instead of waiting for the next commercial break! The shilling has given it a significant hate-base. The interruptions calmed down, though.
Nickelodeon has been extensively advertising Sanjay And Craig. In fact, two or even three commercials for the show will air in a single commercial break. Commercials are even airing on different networks.
This event went so far as to advertise on Tumblr, leading to a backlash against the show because tumblr ads were breaking into the users dashboard.
Nick even loves to interrupt shows with Sanjay and Craig ads as well, playing a commercial right after a show's theme song. However, it's (THANKFULLY) fitted so no content is missed, unlike Studio 10.