Snowdown is the first part of episode 9 in season 2 of Dexter's Laboratory, which first aired on September 10, 1997. In this episode, Dexter uses Dad's skills to combat Dee Dee when she constantly pelts him with snowballs. It is later revealed that Dee Dee got her skills from Mom, who turned out to be a bigger terror than Dad.
Dee Dee is hiding inside a snowman watching as Dexter walks by. She pushes out the snowman's stick and sneaks up behind Dexter. He looks and she throws the snowball directly at his face. Dexter watches in dismay as his sister threatens that she will hit Dexter with a snowball no matter where he is or what he is doing. Dexter looks up in dismay, and Dee Dee hits him with another snowball.
Dexter is hiding behind a tree hoping that Dee Dee wouldn't spot him. He runs toward a couple kissing and hides behind them. Dexter then hides in a snowman and keeps another eye out for Dee Dee. He then hides inside a mailbox and sees he is in the home stretch. Dexter runs toward the house and lunges for the doorknob. He proclaims its safe, but is suddenly buried by a mound of snow. Dee Dee taunts, much to Dexter's humiliation.
Dexter wakes up the next morning, and Dee Dee throws a set of snowballs at him. He then goes to visit Dad to see if he could get advice. Dad then proceeds to tell Dexter a story about how he was the dominating snowball warrior, until he was in college, where he was finally hit with a snowball. Dad then asks Dexter to help reclaim the title. Dexter talks his way out of it, but Dad refuses to let him out. Later, Dad is teaching Dexter how to be the snowball champ, but Dexter's cowardice stops him from learning. Much later, Dexter finally gets the hang of the snowball fight, making Dad proud.
The next day after that, Dexter is watching out for Dee Dee in the hopes of not getting hit by her. Dee Dee appears out of the snow behind her brother with a snowball and throws it at him. Dexter remembers Dad's techniques and counterattacks with a snowball of his own. Dad is proud that his son hit Dee Dee. She herself is proud of Dexter for getting a hit. Dad angrily goes out from behind the tree and orders Dexter to finish the fight. Mom watches from the house window and heads outside. She explains her story of how she defeated Dad and became the new snowball champ. Dad realizes that the whole thing was a charade and everyone laughs. Dee Dee spills the beans about Dexter's lab and he covers her mouth.