Follow That Bird (1985)

"It's big adventure! It's big laughs! It's Big Bird on the big screen!"

Big Bird is sent to live far from Sesame Street by a pesky social worker, who thinks it would be better for him to live with other birds. Unhappy, Big Bird runs away from his foster home, prompting the rest of the Sesame Street gang to go on a cross-country journey to find him.