Probably Diablo's cow levels: https://diablo.fandom.com/wiki/The_Secret_Cow_Level https://diablo.fandom.com/wiki/The_Secret_Cow_Level just because they're fun a

Probably Diablo's cow levels: https://diablo.fandom.com/wiki/The_Secret_Cow_Level https://diablo.fandom.com/wiki/The_Secret_Cow_Level just because they're fun and silly. Or the (defunct) Netscape fishcam that even made it into Firefox for a while: https://en.wikipedia.org/wiki/Fishcam#Netscape https://en.wikipedia.org/wiki/Fishcam#Netscape. Used to watch that for hours a week...