Hacking code in the repl without testing the new behavior. We all did that. Don't lie. Once I wanted to quick fix a "gmail.ca" to "gmail.com", which I did.. but

Hacking code in the repl without testing the new behavior. We all did that. Don't lie. Once I wanted to quick fix a "gmail.ca" to "gmail.com", which I did.. but to all the users instead of just the one mistaken. Fortunately I realized by mistake really fast ;-)