You know who you are.
Part of Editor.exe
TQ had this and it was a dirty trick as it usually ended up crashing the editor…
Because if you’re going to rebuild a world that is as large as gd’s it will take quiet a time until it’s done 
Microsoft Excel often shipped with a flight simulator built in. You could fly around a map and then read the credits. https://www.youtube.com/watch?v=-gYb5GUs0dM
Easter eggs make sure that QA people do their jobs. If it is a menu item, then yes, boredom.