|“||PUNY HUMANS! What's up? I'm gonna suck your brains through these bendy straws!||„|
|~ Mark Chang|
When Timmy wished for an alien monster for him and his friends to play with, Cosmo and Wanda poofed up Mark since they were unable to create one. Mark announced to Timmy and his friends that he plans on sucking out their brains, But Timmy's friends Chester and AJ didn't take him seriously as they thought he was an animatronic. Vicky walked up to Timmy's room and frightened the kids, making Mark fall in love with her for her horrible personality.
Mark was dragged by Vicky to make her a chocolate shake, which were considered dangerous on his planet. While Mark prepared the shake, he encountered and easily captured Chester and AJ. Mark Chang tried to suck their brains out as appetizers for Vicky but he was stopped by Timmy who called Cosmo and Wanda to return him to Yugopotamia.
In Totally Spaced Out, Mark was still mourning the loss of Vicky while celebrating his birthday. Cosmo appeared to help Timmy get Vicky away from him and showed a fake message of Vicky telling Mark to come to him. Mark arrived on Earth and kidnapped Vicky. He tricked Mr. Turner into thinking that Vicky was going to Europe. Timmy later arrived on Yugopotamia and told Mark to give back Vicky. Mark refused and challenged Timmy to a Death Combat.
He chose the first round to take place in the Yugopotamia War Arena. Timmy used a battle gear that shoots pillows to fight Mark since the Yugopotamians hate anything that is fluffly and nice. The alien prince disarmed Timmy and used his robot machine to annihilate Timmy only for it to surprisingly miss. Timmy chose the second round in Flappy Bob's Learnatorium where Mark was panicking about the goodness and niceness in the area, causing him to surrender. Timmy felt bad about Mark so he spared Mark's life and gave him a whack-a-mole machine.
Timmy became Mark's friend when he helped Mark defeat Gigglepies. Mark is also one of the few characters to be aware of Timmy's fairly godparents.