In the movie Captain Underpants: Mega Blissmas, George and Harold, the two mischievous best friends, use a time machine to change some of the traditional Christmas practices they aren't too fond of, such as giving fruitcake and singing carols. However, their actions have unexpected consequences that result in the holiday becoming more bizarre than ever.
Suddenly, Santa Claus is replaced by a robotic version named "Robo-Santa," who plans to take over the world with an army of toys. Meanwhile, the Krampus, a mythical creature who punishes naughty children, joins forces with George and Harold to stop Robo-Santa's evil plans.
Through their wacky adventures, George and Harold learn the true meaning of Christmas and the importance of love, kindness, and friendship. The movie is filled with humor, action, and heartwarming moments that will delight both fans of the Captain Underpants series and new viewers alike.