This article describes a feature in the first Apocalypse Rising
Elf Zombies were the retextures of zombies in Apocalypse Rising. This was done during the 2014 holiday season, and again in 2016. These were the equivalent of civilian zombies, while Santa Zombies were the Christmas versions of the military-type.
Besides the obvious change in outfit, the elf infected produce a jingle sound whenever they move. If they manage to attack a player, a "Ho Ho Ho" sound effect is heard.