There's the friendly
CHUCKLE.
The Big Bang Theory Season 7, Episode 7
(BOTH CHUCKLE)
The Big Bang Theory Season 1, Episode 17
(Leonard and Wolowitz CHUCKLE)
The Big Bang Theory Season 7, Episode 20
(BOTH CHUCKLE)
The Big Bang Theory Season 10, Episode 20
(BOTH CHUCKLE)
The Big Bang Theory Season 2, Episode 9