Successfully complete Pane in the neck with a Silver or better
Submitted by Charizard fan01
To get these two guys, beat the arcade mission "Club soda" under team series A
Submitted by your neighbor
Beat the second stage of the first mission in the arcade league on gold to obtain Dr.Peabody and Crypt Zombie.
Submitted by Phantom of the Opera
In challenge mode beat Day of The Damned on silver to unlock Feeder Zombie
Submitted by Badass Cyborg