Spencer Pratt Threatens to Chop Off Nuts

Only Spencer Pratt would consider a vasectomy to ward off his baby-crazy wife, and only Spencer Pratt wouldn't know it's difficult, if not impossible, to reverse.

Heck, even if it was all elaborately staged for tomorrow's episode of The Hills, only Spencer Pratt would pretend to go to such lengths to avoid having kids.

In a sneak preview released by MTV, he admits that he didn't tell Heidi Montag he looked into the "seven-minute procedure," which he ultimately decided against.

Shocking that he didn't through with it. That would have been the worst medical decision since ... well, you gotta see these Sammy Sosa skin bleaching pictures.

"I thought it was reversible," he tells his wife. "Once I found out it wasn't, I left."

COME TO DADDY: Spencer Pratt wants to fornicate with his mostly plastic wife so bad ... but he wants to get a vasectomy first to make her goalie-pulling tactics moot.

Did he really think you could just have the procedure undone? Is he that stupid, or was that just his explanation for something he obviously wasn't going through with?

Regardless, Heidi Montag is hardly pleased, telling him, "You would have done it right then if you thought it was reversible?" she asks in disbelief. "And then you would have come home and told me 'Hi, honey, I snipped my balls off?'"

Well, there you have that. She raises a fair point.

Check out the clip from The Hills post-jump ...