The Wild Eep is an alert sound from classic Mac OS.
Existent until Mac OS 9, its intonation was extremely weird. Even weirder were the theories suggesting what kind of an animal an eep really was.
From images previously on the website of MacAddict, it appears as an odd form of unicorn.
Eep is an onomatopoeia sound most commonly associated with the Apple Macintosh computer system alert sound "Wild Eep" which was introduced with the Mac System 7 OS, but removed in OS 9. According to Jim Reekes (who was on the Mac OS sound development team at the time), to the best of his knowledge:
- "When System 7 was being created, I collected new sounds. Some of them I made, and some of them I took from a contest. C.K. Haun ([formerly in charge of Apple's Developer group and] now [as of March 30, 2006] in charge of Apple's Developer Technical Services group), submitted one which I think was Wild Eep. It was voted one of the keepers, and we gave him a CD-ROM drive. That's the best I can recall, as this was over ten years ago."
- C.K. adds: It wasn't actually submitted by me  but by someone else. The sound was recorded for a simple game called Dropper by my then-wife Lora Wray/Medina, and can still be heard in the Mac OS X version of the game. This is a raw, unmodified sound that she made one evening while we were watching television, I immediately dragged her to my programming office to record that unique sound for later use. We divorced soon afterwards, and for years I was pestered by hearing her going "Eep!" at me from hundreds of computers on the Apple campus. This sound was even used in a Blockbuster commercial.