The time when we were not aware with advance features of IDE and version control.
(3-4 days before the project demo)

Me: This code was working fine last time. Now it is not compiling. Has anyone did some changes?

Team member: I corrected some spellings. So that our teachers don't correct us at the time of demo.

Me: (shocked, expression less ) We demo the application not the code. And you have not corrected on all the places.

Team member: You should do the rest.

(Based on true story)