Unikitty!

Unikitty (stylized as UniKitty!) is an American-Danish/Canadian animated television series produced by The Lego Group and Warner Bros. Animation for Cartoon Network and starring the character of the same name from The Lego Movie.

Too Many Unikitties
When Unikitty notices that her friends are having a stressful day, she believes everyone should be positive like her. With the help of an invention by Dr. Fox called the Happy Horn, (a model of Unikitty's horn that, when placed on someone's head, it gives them the mindset of Unikitty) that becomes a reality, but she soon starts to realize she misses her friends' old personalities.

https://www.youtube.com/watch?v=jKMLtO6GL-0

https://www.youtube.com/watch?v=6TEIR2utKEQ