Watch Sketches cause time to slow down for everything except Mickey and Oswald (in the sequel). A large pocket watch appears in the air above the targeting cursor and the edges of the screen turn into faded colors. The hands on the watch start at 12 and move clockwise. Once the hands reach 12 again, the time returns to normal. It's great for battling large groups of foes, slowing enviromental hazards, and beating timing-based on puzzles.
It also helps Fairy Sketches last longer while you squirt the item with paint to place where you want it.
In Mickeyjunk Mountain there are hidden alarm clocks. If you paint them, they will have the same effect as the Stop Watch sketch. In the sequel, there are hidden alarm clocks for example in Rainbow Cavern's substation.
Also, in Epic Mickey 2, the Watch Sketch can cause everybody's voice to be a little distorted.