Unlock[]
Mystery egg was unlocked when I used the Book of the Dead twice in a row in the Boss Rush room, so it may have something charmies/orbitals etc. -Frionil (talk) 17:59, 1 May 2018 (UTC)
Mistake?[]
I don't have Book of Dead unlocked yet but I did unlock Mystery Egg so either it was some kind of bug or unlock do have something with charmed enemies and not that item.
Possible Bug[]
When using Extension Cord with Mystery Egg, it works as expected. However, after the charmed enemy is spawned, the electricity doesn't connect to the charmed enemy. It shoots out in random directions connecting to nothing. I think it's a bug. - Sirtimmothybrentwood