Bazinga is an expression of The Big Bang Theory
The Big Bang Theory is a comedy television series about a number of nerds. One of the Nerds (Sheldon Cooper) is not quite of this world and does not understand sarcasm and human contact. If he has a good joke, he ends with the expression: Bazinga. The word actually comes in the place of: Gabriel! It seems to come off of ' zing ' which means that you are fooling someone.
Here some Bazinga's: [YouTube] U85u2ymDl8M [/youtube]