The Rocky Horror Picture Show "Science Fiction/Double Feature"
Duh!!! I think 27+ years is plenty of time to know all the lines of this musical (could be more... I bet my parents went to shows when my mom was pregnant with me). :-)
Since I started going to the monthly Fishnets and Floorshows production, I have been learning all the callback lines, which is part of the audience participation. There are so many callbacks that it takes several shows to learn them. When the time came where I became one of the shadow cast members, my knowledge of the lines and songs worked to my benefit to where all I had to worry about was where I needed to be positioned for each scene.
It has reached the point where, now, if I am watching a clip of The Rocky Horror Picture Show, I am catching myself shouting out the callbacks. Oh, how Fishnets and Floorshows have corrupted me... hehehe.