A sign-off is the end of operations for a radio or television station, generally at the end of each day. Cartoon Network signs off at 9pm every night.
There have been different sign-offs used for Cartoon Network.
In the Powerhouse era, a Next bumper would list Adult Swim. A disclaimer would be shown before Adult Swim starts.
In the Fall era, the sign-off features a boy going through his daily routine. At the end, the Cartoon Network logo is displayed, along with a message saying "Goodnight, see you tomorrow".
In the Noods era, the sign-off features a Nood painting the screen black. The Parental Advisory logo and the Adult Swim disclaimer appear afterwards. Also, a off-screen voice who says "HEY!!!" is heard when a Nood leaves.
In the CHECK it era, these sign-offs are used:
1.0: We see a CHECKlist with Johnny Test, 6teen, Stoked, and Total Drama Action. The menu folds up along with everything else except for the clock. The clock displays the message "Check ya later" before switching to the Cartoon Network logo. There's also another one where the Cartoon Network logo flips to the message "Good Night!" while C and N says "Goodnight!".
2.0: The sign-off displays the message "Hey everybody, that's it for tonight but you could still check out more" before the Cartoon Network logo appears. The sign-off then tells you how to watch more Cartoon Network before the message "Good Night" is displayed.
3.0: Multiple sign-offs are used for CHECK it 3.0. They feature a clip from a show before the Cartoon Network logo appears. There's also another one where Uncle Grandpa's head floats down and then he says "Good morning!".
In Dimensional, a transition brings up the message "Good Night". It changes to "Favorite Shows" and "Tomorrow" before the Cartoon Network logo appears. The announcer says this:
"Okay. Good night, everyone. Thanks for watching your favorite shows. Come back tomorrow for more of your favorites".
The sign-off shows characters from multiple shows. A full version starts with Gumball and Darwin sitting on the couch. Then they're floating. Then we cut to Steven hugging Lion. The Bears are trying to get Panda's phone and pretend they're floating. Then Tulip, One-One and Atticus are seen floating. Victor and Valentino are floating, and Unikitty has his eyes filled with Cartoon Network. Then Craig is seen riding Atticus. Then the Teen Titans appear and Beast Boy wants the pizza, but Cyborg eats it. Gumball and Darwin are seen rocking out in their couch, and Grizzly takes a photo with Bubbles. At the end of the bumper, they form a circle and the Cartoon Network logo appears in the middle. A message saying "Good Night" is displayed. The announcer says this:
"Well, that was an awesome day. Thanks for hanging out, and watching cartoons with us. We'll see you right back here tomorrow, on Cartoon Network. Good night!".