NOT First used on the 'Family Guy'!... the previous definition of 'Gigadity gigadity' is accurate however these words were not first uttered by Quagmire. They were used previously in the Movie 'Can't Hardly Wait' 1998 (pre-dating Family Guy) by the actor Breckin Meyer portraying 'Walter' the band leader at this fucked up party. Seth Green (who we all know does several voices and has a lot of creative input in Family Guy) also stars in this movie.
"and then I did your girlfriend!---Gigady Gigady!" (I don't actually remember the fucken exact words... steal the movie and see for your fricken self tough guy!)