The phrase originally included, "*ding dong*", "Pizza Delivery", and "bwah-chicka-bwah-bwah" (in that order) as a representation of how a typical low-budget adult film would begin. It was later shortened to just "bwah-chicka-bwah-bwah".
Poster #2: Pizza Delivery!
Poster #1: bwah-chicka-bwah-bwah!
Poster #2: LOL
You know what I'm sayin'! Last night I got me some bwah-chicka-bwah-bwah!