In episode 24 of JoJo's Bizarre Adventure: Stardust Crusaders, Polnareff takes advantage of a dangerous situation to show off his knowledge of hand signals. A video of this can be found here.
Kakyoin recognises the hand signal as meaning "Your underwear is showing", which greatly pleases Polnareff. The two of them share some kind of elaborate handshake to mark the occasion, the eyes of both characters being darkened (which, as far as I understand, usually indicates seriousness).
What on Earth is going on here? Why do Kakyoin and Polnareff know this, why is Polnareff so pleased and why do they share an elaborate hand shake afterwards?