It's an Addiciton

"In Den Endkampf, get your fix."

- Achievement description

 is an achievement in the Zombies map Den Endkampf. It requires players to Pack-A-Punch or Perk-A-Punch five times in total.

Trivia

 * 'Foster the Zombies' is a parody of the band 'Foster the People'. All achievements to do with Den Endkampf have something to do with the Key of Awesome's parody of their song 'Pumped Up Kicks'.
 * is a reference to the line of the same words.