Koosalagoopagoop is the second part of the 21st episode of Dexter's Laboratory. In this episode, Dee Dee's imaginary friend Koosalagoopagoop tells about being the king of Koosland.
Koosalagoopagoop lies to Dee Dee about being the king of Koosland and goes through a lot of trouble keeping her away from the truth when she goes to Koosland herself.
The episode begins with Dee Dee standing still. Her head starts shaking and then a bunch of rainbows and magic burst out of her head and into the world. There, Koosalagoopagoop is seen laying down and sleeping in Dee Dee's imagination land. Dee Dee wakes him and they start to dance and play. The Koosalagoopagoop Theme Song starts playing and Koosalagoopagoop introduces himself to the audience. After the song ends, Dee Dee is seen sleeping in her bed. She wakes up and states that she can't sleep, and she finds Koosy standing there. Koosy tells her a story about the land he comes from called Koosland. Dee Dee is mesmerized by the story and dreams of how magical and amazing Koosland must be. Koosy then tells her that he king of Koosland is himself. However, Koosy is lying about this and Dee Dee believes him. Dee Dee screams in joy and begs him to take her to Koosland. Koosalagoopagoop sweats and fearfully tells her that she can't go to Koosland. Disappointed, Dee Dee sadly walks back to her bed to go to sleep, but then she suddenly and quickly jets off into the heart on Koosy's stomach which is a portal to Koosland. Terrified, Koosalagoopagoop bends down in there and chases after her.