the stuff legends are made of

That which is or will be famous, renowned, or well remembered due to being especially remarkable or extraordinary. The team made an absolutely incredible comeback, overcoming a 20-point deficit in the final minutes of the game. I tell you, it was the stuff legends are made of. You remember Jenny's 30th birthday party, right? Gosh, that night was the stuff legends are made of—I've never had so much fun in my entire life!