What was Santa's favorite subject in school?

The Christmas joke “What was Santa’s favorite subject in school? Chemis-tree!” is a pun that combines the field of chemistry with the Christmas-related concept of a tree. Chemistry is a branch of science focused on the study of substances, their properties, and how they interact. The pun is created by replacing the end of “chemistry” with “tree,” forming “chemis-tree.” The humor arises from this playful blending of a school subject with a symbol commonly associated with Christmas (a tree), which is Santa Claus’s domain. The joke relies on the similarity in sound between “chemistry” and “chemis-tree,” creating a lighthearted and whimsical connection that is fitting for a character associated with the holiday season.