Frosty the Snowman (character)

He is a snowman that appeared in "Phineas and Ferb Christmas Vacation", after Ferb wonders were Perry is, Perry appears walikng through the snow, then, he puts a top hat on a snowman. The snowman comes to life and tells Perry "Wintertime's fun. Follow me!" A loud crash is heard, and the poor snowman's nose rolls over to Perry. He is next shown exiting the Agency's elevator into The Agency Christmas party, still holding the carrot

There is a christmas carol about him, and, a variation of it was performed by Monogram and Carl in "Phineas and Ferb Holiday Favorites"