Army Men II
Dr. Madd appears at the end, where he is shown to have recovered Major Mylar's remains so he can piece him together.
Army Men: Sarge's Heroes
Dr. Madd was apparently enlisted by the Tan Republic to create zombies from them from the remains of Green, Grey and Red soldiers. Several of Madd's creations menace Sarge during his mission to rescue Shrap.
Army Men: Sarge's Heroes 2
Several zombies created by Dr. Madd appear in the graveyard level to attack the Greens. Madd himself can be seen in the middle of the map though, if shot at, he will simply teleport away.