"Luck's a lady... apparently she's a bit of a slut where I'm concerned."
Half of what Sean says could count as this, and especially Dr. Kwong's missions.
Leaping off the top of the Eiffel Tower and hearing Sean yelp like a girl is always laugh-worthy.
Unintentionally invoked: When entering a hiding spot, Sean speaks one of several stock phrases, which can have unintentionally hilarious consequences, especially when the hiding spot is a 'Kiss The Girl' type.
"Down the hatch, as they say!"
The descriptions for the weapons, cars and perks. I mean, how often does one get to compare the MP-40 to a hooker?