Someone posted on Shooting People's daily bulletin asking how you could create the effect of someone wetting themselves on cue. Today they got two quite different responses:

"I did this on a film about 6 months ago and it worked beautifully. Basically it was a 500ml empty soft drinks bottle with a tube attached (the tube in question was from a water filled skipping rope, Toys R Us!. With a hole drilled in the cap and the tube tightly fitted, it was placed on the actors back and taped onto him, under his clothes, pointing down. The other end of the tube ran into his trouser pocket with a small stopper in the end. On cue, he reached in his pocket, pulled out the stopper and the water flowed. Movie magic! For the cost of about £5."
From Ricardo Lacombe

" Whatever happened to method acting? Get the actor to drink lots of water, at least a litre or two, about half an hour before the shoot and let nature take its course. It should be water and not other beverages as it passes through the system much quicker. "
From Chris Patmore

While we appreciate the lengths that actors go to to create a moving, believeable performance, we'd go with the former approach.