| The subject of this article is non-canonical.|
While created as part of licensed material, it has not been confirmed as part of the "real" Buffyverse.
A MacGuffin was a type of mystical creature. The Watchers traditionally selected two of these, which formed a puzzle that gave to their Slayers to test their skills.
While Buffy Summers was on summer vacation at her father's house in Los Angeles, two MacGuffins made a bet with Rupert Giles that she could beat the 561 A.D. record of the Slayer, Garnhuld, by two days. She beat the record, but fell two hours short of winning the bet for Giles. After solving the puzzle, Buffy sent the MacGuffins back to Giles to get even.
The trick to make them passive was to slam them into each other, which caused the MacGuffins to interlock.