This has only been tried with Wario, but will probably work with any character. Go to Tick Tock Clock, and try to freeze the time - this makes it easier. To freeze the time, enter the clock at any o'clock. Climb up the level until you reach the area where there are three things that spring out from the walls, with a yellow grate above them (which houses a block with ten coins). They should be extended outwards so that there is just a little bit of squeeze space to get past them (if not, you may need to exit and then reenter the level). Go past them and then jump onto the edge of the grating above the springy thing so that you grab it and hang off of it. Then, fall off of it. You should land on the spring thing and have the grating going through your midsection. Walk forwards and you will fall through it; jump and you'll go on top of it.
Submitted by: kornyhatemachine