Major Cass was a character who made an appearance in the Season 10 episode of the CBS-TV series M*A*S*H titled "'Twas The Day After Christmas". The part of the Major was played by actor Michael Ensign.
About Cass and "Boxing Day" at the 4077th[]
When the 4077th is celebrating Christmas with a regiment of British troops, several British G.I.s mention a British Army "Boxing Day" tradition where enlisted men change places with the Officers for a day, it is Major Cass, the commander of the British soldiers, who suggests to Klinger, who is all for trying it, and Potter that the 4077th try it out, too. Cass said it worked wonders for the morale of his unit.