Absolute classic if anybody else is interested in reading:

https://users.cs.utah.edu/~elb/folklore/mel.html

Mel was for sure on another level:

It was a long time before I understood that remark. Since Mel knew the numerical value of every operation code, and assigned his own drum addresses, every instruction he wrote could also be considered a numerical constant. He could pick up an earlier "add" instruction, say, and multiply by it, if it had the right numeric value. His code was not easy for someone else to modify.