When a bowler oversteps (or in rare cases, has the back foot touching the return crease) during the delivery stride, the umpire usually calls a no ball while the ball is still in play. On hearing this call, both batsmen could pluck out all three stumps at their end, and run with them to score runs for as long as they like!
From Law 28 (The Wicket is down) (quoted below), the fielding side won't be able to remake the wicket, so neither batsman can be run out. Without doubt, the batsmen doing this would be considered against spirit of the game, but is there anything in the Laws which prohibit it?
1. Wicket put down
(a) The wicket is put down if a bail is completely removed from the top of the stumps, or a stump is struck out of the ground,
The wicket is also put down if a fielder strikes or pulls a stump out of the ground in the same manner.
3. Remaking wicket
If a wicket is broken or put down while the ball is in play, it shall not be remade by an umpire until the ball is dead. See Law 23 (Dead ball). Any fielder may, however, while the ball is in play,
(i) replace a bail or bails on top of the stumps.
(ii) put back one or more stumps into the ground where the wicket originally stood.