In Unit 10, by defeating the Makron, go down into a corridor, shoot the crack at the end of this corridor, to reveal the ID gallery, go down this room, and a door covering a hole in the ground will explode. Go around, and you will find a Tank sitting down, with two Iron Maidens. There is strange music playing. Next to them on each side are two crying Marines. The Iron Maidens will gasp, rub and tickle the Tank.
however,there is a rumor that the tank and The Iron Maidens survived the exsplosion.
^and that they were the parents of Tank Jr. from the next game