2021

1

 * Ed, Edd n Eddy, Courage the Cowardly Dog, Codename: Kids Next Door, The Grim Adventures of Billy & Mandy, and Long Live the Royals were added to HBO Max.

8

 * Teen Titans Go! began its seventh season and aired its 300th episode.

18

 * Craig of the Creek aired its half-hour special "Winter Break".
 * The movie Justice League made it's network premiere.

5

 * A major restructuring of Cartoon Network was announced, including a new preschool block, a family block, and a girls' block.

7

 * We Bare Bears: The Movie was added to HBO Max.

20

 * Tom and Jerry Special Shorts was released on HBO Max.

25

 * Close Enough released its second season on HBO Max.
 * Scooby-Doo and Guess Who? ended the first half of its second season on Boomerang before moving to HBO Max.

28

 * Craig of the Creek has a 24 hour marathon to celebrate the final day of Black History Month.

6

 * Elliott from Earth premiered in the UK.

11

 * Tig n' Seek released its second season on HBO Max.

27

 * Total DramaRama aired its season two finale.

29

 * Elliott from Earth aired as a two-week series premiere in the US.
 * Spring Breakaway begins.

1

 * The logo was changed to "Cat-toon Network" for April Fools' Day.

2

 * Despicable Me made it's network premiere.

3

 * Total DramaRama aired its season three premiere.

5

 * Despicable Me 2 made it's network premiere.

9

 * Ben 10 aired its first one-hour movie event titled: "Ben 10,010", thus airing its fifth and final season.
 * Elliott from Earth aired its season one finale.

10

 * Ben 10 aired its second one-hour movie event titled: "Ben Gen 10", being a crossover with Generator Rex.

11

 * Ben 10 aired its third and final one-hour movie event titled: "Alien X-Tinction", thus airing its final episode and series finale.
 * Spring Breakaway ended.

15

 * Infinity Train released its fourth and final season titled: "Book Four: Duet" on HBO Max, thus releasing its final episodes and series finale.

22

 * Captain Planet and the Planeteers takes over Boomerang throughout the entire day, while Craig of the Creek takes over Cartoon Network starting at 10:00 a.m., in honor of Earth Day.

29

 * Looney Tunes Cartoons released its season one finale on HBO Max.

1

 * Teen Titans GO! aired its season six finale.

3

 * The Looney Tunes Show celebrates its 10th anniversary

9

 * The Amazing World of Gumball celebrates its 10th anniversary.

20

 * Adventure Time: Distant Lands released its third special, "Together Again" on HBO Max.

29

 * Victor and Valentino aired its season two finale.

3

 * The Fungies! released its second season on HBO Max.

4

 * The Fungies! made its debut on Cartoon Network.

6

 * DC Super Hero Girls aired its season two premiere.

17

 * Summer Camp Island released its fourth season on HBO Max.

20

 * Teen Titans Go! See Space Jam aired.

1

 * Tom and Jerry in New York released its series premiere on HBO Max.

2

 * Craig of the Creek aired its season three finale.

5

 * Looney Tunes Cartoons made its debut on Cartoon Network.
 * Total DramaRama returns with new episodes

8

 * Looney Tunes Cartoons released its season two premiere on HBO Max.

16

 * Johnny Test returned for its seventh season on Netflix.
 * Looney Tunes Cartoons was removed from Cartoon Network.

29

 * Jellystone! released its series premiere on HBO Max.

1

 * OK K.O.! Let's Be Heroes celebrate its 4th anniversary.

6

 * Tig n' Seek made its debut on Cartoon Network.

19

 * Looney Tunes Cartoons released its back to school special, thus releasing its season two finale on HBO Max.

20

 * Tig n' Seek aired its season two premiere on Cartoon Network.

2

 * Adventure Time: Distant Lands released its fourth and final special, "Wizard City", on HBO Max.

4

 * Jellystone! made its debut on Cartoon Network.
 * Victor and Valentino aired its season three premiere.

10

 * Elliott from Earth was added to HBO Max.

13

 * Cartoonito launched on Cartoon Network and HBO Max.
 * Thomas & Friends: All Engines Go aired as a series premiere on Cartoon Network.
 * Baby Looney Tunes aired reruns on Cartoon Network.
 * Bing aired reruns on Cartoon Network.
 * Caillou aired reruns on Cartoon Network.
 * Mush-Mush and the Mushables aired as a series premiere on Cartoon Network.
 * Pocoyo aired as a series premiere on Cartoon Network.
 * Little Ellen released its series premiere on HBO Max.

14

 * Straight Outta Nowhere: Scooby-Doo! Meets Courage the Cowardly Dog was released on DVD and Digital Video.

16

 * Tig n' Seek released its third season on HBO Max.

18

 * Lucas the Spider aired as a series premiere on Cartoon Network.
 * Esme & Roy made its debut on Cartoon Network.
 * Family Guy left Adult Swim after airing reruns for 18 years.

19

 * Love Monster aired as a series premiere on Cartoon Network.
 * Care Bears: Unlock the Magic aired reruns on Cartoon Network.
 * ACME Night launched on Cartoon Network with the premiere of Shazam!.

20

 * Total DramaRama was added to HBO Max.

26

 * Man of Steel made it's network premiere.

30

 * Yabba-Dabba Dinosaurs released its series premiere on HBO Max.

1

 * Cartoon Network celebrated its 29th anniversary.
 * Teen Titans Go! vs. Teen Titans and Be Cool, Scooby-Doo! were added to HBO Max.
 * Scooby-Doo and Guess Who? released the second half of its second season on HBO Max.

3

 * Teenage Mutant Ninja Turtles made its network premiere.

10

 * Ready Player One made its network premiere.

14

 * Aquaman: King of Atlantis released its miniseries premiere on HBO Max.
 * Teen Titans Go! was added to HBO Max.

21

 * Jellystone! released its Halloween special "Spell Book" on HBO Max.

24

 * Scoob! made its network premiere.

25

 * Craig of the Creek aired its season four premiere.
 * Close Enough made its debut on TBS.

28

 * Aquaman: King of Atlantis released its miniseries finale on HBO Max.

31

 * The Amazing Spider-Man made its network premiere.

4

 * Steven Universe celebrated its 8th anniversary.

13

 * Darwin's Yearbook was added to HBO Max.

14

 * Spider-Man 2 made its network premiere.

18

 * The Powerpuff Girls celebrated its 23rd anniversary.
 * Tom and Jerry in New York released its second season on HBO Max.

21

 * Spider-Man 3 made its network premiere.

25

 * Looney Tunes Cartoons released its third season on HBO Max.
 * We Baby Bears trailer is released on YouTube channel.

28

 * Minions made its network premiere.
 * Harry Potter: Hogwarts Tournament of Houses aired its premiere on TBS and Cartoon Network.

2

 * Odo released its series premiere on HBO Max.

7

 * Apple & Onion aired its series finale

9

 * Summer Camp Island released its fifth season on HBO Max.

13

 * Close Enough aired its season one finale on TBS.

15

 * What's New, Scooby-Doo? was added to HBO Max.

16

 * The Fungies! released its third and final season on HBO Max, thus releasing its final episodes and series finale.

19

 * Harry Potter: Hogwarts Tournament of Houses aired its finale on TBS and Cartoon Network.

27

 * After 14 years break, Futurama is returned on Adult Swim block.