This page documents interesting observations in VVVVVV.
Fade bars are processed during unfocus pause
The unfocus pause was a new feature added in 2.1, where the game would automatically pause while being unfocused. It was implemented by putting a conditional in the game loop that stops most game logic if the window loses focus.
Except the function to process the timers of the fade-in/fade-out animation,
graphics.processfade(), was put outside the conditional. So the fade bar timer actually gets processed during the unfocus pause, meaning if you have a fade-in/fade-out animation running and unfocus the game, you can finish its timer without any time passing in-game.