Do you know anyone whose laugh makes YOU laugh, and you have no idea what's even funny?

My sister's laugh is extremely infectious to anyone who overhears her, and when she's laughing really hard, it comes out as "Yek yek yek." Anyone nearby has tears coming out of their eyes from laughing at her laughter. I also have a co-worker whose laugh is always, "Hee how hmm hmm." You hear that 3 times in a row and you're on the floor. He has no idea we're laughing harder at him than the original funny thing. How about for you?