What is a PhD Flopper?

A PhD Flopper is a perk that allows the player to ignore self-inflicted damage, including damage from falling and explosives. It appears in the zombie game modes of "Call of Duty: Black Ops" and "Call of Duty: Black Ops II."

On the map called "Buried," PhD Flopper is a hidden, permanent perk that can only be obtained if a player jumps from a high location and takes falling damage. There, it serves as a recreation of the perk that can normally be obtained via Perk-a-Cola dispenser. The perk also lets the player create a powerful explosion upon landing, as long as the player dives into a prone position while falling toward the ground.