Gary (2008)

Gary is entering in his teens and has a crush on Valentine, who is much taller and more sexually developed than he is. He is attracted to her and would like to kiss and romance her, but he feels insecure and dreams of becoming an adult to do so. Gary draws an adult version of himself on the wall of his room hoping to be that guy once. When his wish comes true and adult Gary comes to life from the wall, Gary comes to regret it.

Unfortunately the movie Gary is not yet available on HBO Max.