A phrase made popular by one Jared Hopkins. After a person tells a long story that can be easily understood by anyone he adds in his trademark phrase, "I don't get." Some laugh, while others don't get his not getting. They often try to simplify their already understood story which only serves to increase laughter.
Cara: "...and that's what happened."
Jared: "I don't get it"
Erin: "What didn't you get about it?"