I just booted a very old system with a SUSE 10 floppy disk and instead of the standard theme for the installation boot menu thing, there was a rather festive Lemmings-like level in the background with a snowy winter scene (but, with Tuxes rather than Lemmings). Reminds me of the Linux game Pingus... :)
I would have posted a screenshot, but I had to reboot the machine and on reboot it was back to the default SUSE screen again. Easter egg? Don't know why I couldn't get it to work the second time, though. :)