Clifford (1994)

When his brother asks him to look after his young son, Clifford (Martin Short), Martin Daniels (Charles Grodin) agrees, taking the boy into his home and introducing him to his future wife, Sarah (Mary Steenburgen). Clifford is fixated on the idea of visiting a famed theme park, and Martin, an engineer who helped build the park, makes plans to take him. But, when Clifford reveals himself to be a first-rate brat, his uncle goes bonkers, and a loony inter-generational standoff ensues.