Your friend Robert who always makes funny observations and light-hearted quips? He’s jocose, meaning he's good humored and jokes around a lot.
Latin may not seem like a lot of laughs sometimes, but it is responsible for injecting a little humor into English words that have their origins in jocus, the Latin word meaning "joke" or "jest." Jocose, jocular, joke — they all come from jocus. Jocose first came into English in the seventeenth century as a way to describe something that’s characterized by a playful, merry humor.