The Cartoon Network series that spun off from The Lego Movie franchise in 2017 was Unikitty!. The show centers on Unikitty, the cheerful ruler of the Unikingdom, who first appeared as a supporting character in The Lego Movie (2014).
Warner Bros. and Lego announced the spin-off in May 2017. Cartoon Network aired preview episodes later that year, while the series received its official U.S. premiere on January 1, 2018. That timing can cause confusion, but the 2017 date refers to the spin-off’s announcement and early previews.
The series expanded Unikitty’s world with her brother Prince Puppycorn, scientist Dr. Fox, bodyguard Hawkodile, adviser Richard, and the villain Master Frown. Tara Strong voiced Unikitty, whose energetic personality was adapted for short, fast-paced animated adventures.
Unikitty! ran for three seasons and 104 episodes, concluding in 2020. It is sometimes confused with other Lego television projects, but Mixels was a separate Cartoon Network series and Teen Titans Go! was not a Lego Movie spin-off.