What is a single word or phrase for someone who intentionally misses the point?

This guy is being a smart-ass. The term can be used to describe someone who is irritatingly clever or smug. His "jokes" are about things beyond the topic at hand, and tend to be a little on the rude side. He's deliberately ignoring the focus of the conversation to satisfy himself with his own wittiness, which other people find less amusing.

You could say "He/She is being deliberately obtuse".

obtuse

Annoyingly insensitive or slow to understand:

Oxford Dictionary

The apparently dull-witted but actually quite astute Lt. Columbo (Peter Falk) was accused of this once by a frustrated suspect.

"Are you actually this stupid, or are you just being deliberately obtuse?"

These guys are obviously "playing dumb" so as to be comical and provoke laughter.

• play dumb - "to pretend to not know or not understand something"

Examples:

• "He was playing dumb only to be funny."
• "Don’t play dumb with me – I know you took the money."
• "She said she would play dumb if challenged by a police officer."

Your coworker is making offhand comments.

Ungraciously or offensively nonchalant or cool in manner.

(Oxford Living Dictionaries)