The Grim Adventures of Billy and Mandy (2001)

Season 3: Episode 32

Thanks to Mandy, Billy decides to get rid of his "Dinobonoid" action figures thinking he is too old for them. Grim makes the toys come to life, and shrinks Billy to their size so he can have a last adventure with them. The "Jurassic Creeps" become aware of Grim's scythe and steal it from him to use its powers to rule the world; however, the magic that made them come alive runs out just in time, and the toys become inanimate once again. Billy reverts to his normal size too, but he stays trapped inside the box in which the action figures came.