A popular comedy routine in silent films involved a man tearing his pants as he strutted around a crowded dance floor. The earliest known version of the routine was performed by Max Linder in a 1908 film simply titled Torn Trousers.
Later versions incorporated one contrivance or another that led to the man losing his pants entirely. The evolution of the routine culminated in the famous party scene of Harold Lloyd's The Freshman (1925).
Dropping trou is no longer exclusive to men. A recent update of the routine featured on the BBC series Miranda placed a woman (Miranda Hart) into this embarrassing situation ("Date," 2009). Hart's character figures that she can readjust her pants without being noticed by keeping to the rhythm of the music.