Add a further comment to the Scooby-Doo part for Cartoon Network: for a while they would also take any moment they can to play Scooby-Doo movies at any chance they can. That and Johnny Test.
Ironically, since at least 2010, there has been less and less Scooby-Doo airtime on the American Cartoon Network channel. The pre-1990s shows have not been seen on the network since early 2010, and the only Scooby-Doo programming seen on the channel since then has been the more inferior What's New, Scooby-Doo? and the more controversialScooby-Doo! Mystery Incorporated, usually once or twice a weekday. The Scooby-Doo movies are also not played very often, and when they are, they are usually the more recent ones.
Boomerang, at least in the UK, held what it called a Scooby Summer sometime during the 2000's. For the entirety of the summer holidays, every waking hour in the schedule would be filled by Scooby-Doo. It might have been the longest marathon of any cartoon ever, complete with adverts berating the viewers and making it seem like it was their fault! Even today, as of 2011, Boomerang will be having a "Scooby Week" or two, using excuses such as Easter break and midterms.
Planet 51 is shown regularly on Cartoon Network for seemingly no reason at very random times of the day.
From '99 to 2005 you could not go one day without seeing either Dexter's Laboratory or The Powerpuff Girls playing on the network. Both of these shows were practically CN's mascots during that time, to the point that when Cartoon Network finally canceled Looney Tunes in 2004 it was replaced by Dexter reruns.
Also, in the mid-2000s, they would show nothing but Codename: Kids Next Door back to back on Saturday mornings. The show also replaced Looney Tunes and other classic cartoons as "Toon Extras" in early 2004.
Ed, Edd n Eddy is certainly worth a mention. Since its debut in January 1999, it has been a big hit on Cartoon Network, has aired a total of 70 episodes running through 5 and 1/4 seasons and a series-ending movie and, even after being out of production for years, it still airs at least 2 episodes every Monday-Friday. Suffice it to say, it is admired by both viewers and CN.
Courage the Cowardly Dog became the new 'it' show during and after the reign of PPG and Dexter's Lab, then, even after it was cancelled, it came back recently and could be seen airing every day for a time during 2010 and early 2011, though that's since ceased. It has since returned in 2013 as part of Cartoon Network's regular programming. For some reason, ever since Courage was rerun, "The Curse of Ramses" would show more often than any other episode by a substantial margin.
The original Ben 10 used to be like this. The sequels, on the other hand, tend to only be shown a couple times a week.
It's a different story in the UK, as (along with Chowder and Johnny Test) Ben 10 and Ben 10: Alien Force dominate the channel. It's got to the point where the late evening 'Cartoon Cartoon' show now consists of nothing but Chowder and Ben 10: Alien Force reruns.
An odd example with Ben 10: Omniverse, which has daily slots on Boomerang, despite still being in production on Cartoon Network proper.
Adventure Time. In addition to weekly marathons, it's used to round out most 15-minute blocks left over after movies.
Both of the Fionna and Cake episodes were heavily promoted, countdown clock and all. The CN site even changed the link with Finn's face on it to Fionna's during its premiere week! It even has its own web game and DVD now, the ads for both being commonly seen.
For the CN Real block, the scheduling wasn't so bad; the live-action shows mainly stayed within the block. However, they were endlessly promoted over every cartoon, and the kicker was a video featuring Andrew W.K. proudly proclaiming that Cartoon Network was more than just cartoons.
The Marvelous Misadventures of Flapjack was hit with this literally from the instant it premiered — CN started airing it multiple times per day even though there was only one episode. Ironic, given that CN stopped caring halfway through the second season.
The Amazing World of Gumball. Huge, huge buildup: They showed a "sneak peek" of it six days before its premiere. The day it debuted, there was a countdown bug on screen. And already it's averaging at least one rerun a day.
As of October 2014 Gumball averages at least 8 - 10 repeats every weekday. It and Teen Titans Go (also averaging 8 episodes daily) are commonly used whenever Cartoon Network seemingly needs schedule filler.
The Looney Tunes Show seems to be this as well, in that, like Adventure Time above, its "Merrie Melodies" segments are occasionally used to round out the minutes after other shows. Also, like The Amazing World of Gumball, there was a countdown bug on the screen the day it premiered. Also, during the 4th of July weekend of 2011, the network aired random episodes of the show that were supposedly made up until that point, along with random airings of classic Looney Tunes shorts, Space Jam, and Looney Tunes: Back in Action in continuous loops. Back in the day, they used to have "June Bugs", a 72-hour block in June, consisting of nothing but Bugs Bunny cartoons. The final regular June Bugs marathon was in 2002 until it got a semi-revival in 2013.
Hi Hi Puffy AmiYumi got hit with this during its heyday. CN gave it major promotion, marathons, a prime time premiere slot, daily reruns, merchandising, and even a parade float for the Macy's Thanksgiving Day Parade in 2005 (with Puffy Ami Yumi themselves performing!). This was all an attempt to make this show the next Powerpuff Girls. By the third season, however, they stopped caring about it.
Captain Planet and the Planeteers was transmitted day and night. In Latin America, it was transmitted during weekends (the time of the day kids are mostly free) for four hours in a row. It's one of the reasons why such a light-hearted series could triumph during the Dark Age.
Nowadays, Regular Show seems to be heading this way, to the point of airing it 3 times a day on Tuesday afternoons.
That's nothing compared to today. As of August 2014, it airs 3 to 5 times a day on the schedule. It's not to the extent of otherCNshows, but it's still alot.
Total Drama, seasonally. You won't find it in the Winter. But when Spring/Summer comes, it comes back in full force with a new season. Heck, CN is actually willing to sacrifice an hour of Johnny Test for its previous seasons to prepare for the new one.
During the second part of the fifth season, CN showed at least one new episode a weekday, sometimes even two, hyping it as a "Summer Showdown". The same would happen to the entirety of its sixth season.
The High Fructose Adventures of The Annoying Orange. Like with Gumball, there was a "sneak peek" of a Star Trek parody episode two weeks before it was to officially premiere. Said sneak peek episode went on to be rerun once a day for at least a week. Countdown bugs on the screen for the whole day of both the sneak peek and the actual premiere.
Oh, Johnny Test. Hated by many and loved by nobody except the execs, the series managed to last for 9 years with 6 seasons and retain heavy advertising despite having a very loud hatedom begging for its cancellation (a hatedom that only grew after it replaced DC Nation!). Before the show officially ended in its native Canada, their cries seemed to go unheard, perhaps due to how cheap the animation is for Johnny Test - even if the bare minimum of people are watching it, they still make a profit! Since the show ended though, CN would only air it for one hour early in the morning in May, get rid of its slot on weekdays in June and July, and in September, the show was completely gone.
Ninjago seems to have become this, mainly due to the success of its accompanying toyline.
Speaking of Boomerang, they decided to devote weekdays and entire weekends to nothing but The Flintstones. To the point where it gets so bad that if you here the theme song one more freakin' time you'll scream.
[adult swim] at one point began airing Squidbillies every weeknight at midnight while airing commercials stating it was getting low ratings and berating the viewers for not watching this awesome show.
Adult Swim absolutely loves Fox reruns, specifically King of the Hill and anyshowmade by Seth MacFarlane. Weekdays are King of the Hill, American Dad, and Family Guy for 6 of its 9 hours (including repeats). In one week, there is going to be 14 hours of King of the Hill, 12.5 hours of Family Guy, and 10 hours of American Dad for a total of 36.5 hours.
Adult Swim lost the rights to air Futurama at the end of 2007. In the days leading up to New Year's Day 2008, they showed every episode in existence at that point in a row.
Futurama would later be the network favorite for Comedy Central when they renewed the series. Not only did it get at least one airing every weekday at 1:30 (Along with the regular airing at 9:00 PM before their precious South Park), but it also got another 26 episode renewal bringing the show's run up to 2013 along with promotion and a nice 10:00 PM slot. They love the show just as much as Adult Swim did.
One could almost say they love the show just as much as South Park. Perhaps even more, given how much air time it gets.
Adult Swim has also been playing The Oblongs pretty regularly, off and on, since 2002, sometimes even 4 or 5 days a week, despite the show only having 13 episodes.
Robot Chicken has consistently aired two eps a night at midnight on Adult Swim's weeknight block (excluding Thursdays) since at least 2010, and at one point was used as the lead-in to the entire Sunday night block. This status was eventually lampshaded by having AS execs Keith Crofford and Mike Lazzo appear in the 100th episode to fight the Robot Chicken during his rampage through the castle, only to be easily killed. Crofford's last words:
The ratings we'll get for this will be huge...
Adult Swim appears to be going all-in on Rick and Morty. As of May 10th, 2014, they show only one episode per week (on Sunday nights), but they show it twice per rotation, at 9 PM and Midnight. When combined with the repeat run, this means that the same episode of the show airs four times on the same day. Of course, given the quality of the show, and the fact that, because of this, it's very easy to actually watch, I'm sure very few people are complaining about it.
Dragons: Riders of Berk, like other shows introduced to the network since 2010, got the sneak-peak hour-long episode which was then re-aired every day for a week, the countdown bug on the screen for the actual premiere, and, again, the currently most-recent episode is re-aired at least once every day for a week until the next episode premieres, to the point that it briefly took over Cartoon Planet's timeslot to air reruns.
The show eventually took over DC Nation's timeslot for reruns on Saturdays, with Johnny Test on Sundays, while the actual DC Nation was on hiatus, and the network of course didn't tell any of the creators about this.
During the holidays, you can rarely turn on Cartoon Network without seeing Grandma Got Run Over by a Reindeer. As mentioned on its Trivia page, it airs so much that if one hears the titular theme again, they'll scream.
They have some sort of odd fixation to airing Tom and Jerry: The Magic Ring on most weekends. This has been happening since 2005.
Teen Titans Go!, to no one's surprise being the comedy half of the DC Nation lineup, quickly fell into this. Its DC Nation slot is a rerun, with a primetime slot showing new episodes. Ads for it show constantly, while Beware the Batman has Invisible Advertising. CN even runs marathons of it to fill up the daytime schedule. In just a few episodes the Network already ordered a second season, while Beware got pulled from DC Nation entirely (supposedly scheduled for a January return, until CN pushed it to an unspecified "first half of 2014" return), all but guaranteeing the latter is gonna get the axe considering how littleCartoon Network thinks of Action Cartoons.
As of August 2014, the show is now airing six times a day on the weekdays, despite only having 29 half-hour episodes! Even CN's other hits like Adventure Time and Gumball don't receive that many airings in one day.
With Cartoon Network's flicks, Diary of a Wimpy Kid has been aired a lot, almost once every four or five weeks.
For what it counts, even commercials for the films got a lot of airtime - to the point that the same commercial for Rodrick Rules would often play three or more times in a row.
Prior to its premiere, Cartoon Network was seriously hyping up Uncle Grandpa as is pretty typical for first-run shows. On its premiere, forty-five minutes after the pilot episode, Cartoon Network even showed the pilot again, replacing The Annoying Orange's timeslot.