Flair was-is one of the best at committing his character and to his gimmick. Although, if you do some research, the "Nature Boy" had a reputation just as storied as his character.
The first time I heard of or saw a Whataburger was in the 1994 movie 8 Seconds. Luke Perry played bull rider Lane Frost and in the scene, Lane takes his girlfriend Kellie to the restaurant on a date. I can't remember the conversation but he asks "are you going to finish your 'Whatachickn'?" My interest was piqued in overdrive.