You need to replace the soap with game themed soap, like http://www.etsy.com/listing/82955296/nes-nintendo-controller-soap-green-apple
Yeah I've seen those before. I was tempted at first, but I just don't like "decorative soap". I like functional things. So having a bar of soap there that you can use technically, but never really do use, bothers me. So I decided against that. I would, however, love to find a Super Mario soap dispenser. Seems like there's Mario memorabilia out there for everything, but I couldn't find a dispenser. If someone finds one let me know!

How are the sound effects handled? What do you use for the triggers?
There is a seller on ebay named bigdawgsgreetings that offers sound making devices. Here is one that I used for when the lights get turned on. That specific sound is just triggered by light.
LinkThen here is a 5 button one that I used for the toilet:
Link2First, I removed the batteries and I plugged the USB's into a USB to wall outlet converter. I did this because it's a permanent installation and I didn't want to mess with batteries. Then I cut off the provided speakers. I then hacked an old set of PC speakers and I wired the lines that were going to the provided speakers and make them go to the PC speakers instead. This made the sounds much louder and controllable. Then for the toilet I hacked off the buttons on the one sound unit. I wired them up to some leaf switches. Something similar to these, although any could work.
LinkThen I had to rig up a little contraption inside the toilet box what when the toilet is flushed it would hit the leaf switch and trigger the sounds. I could post a picture later if there's really a desire to see it. But it's going to be different for other toilets since the innards can vary based on what type of toilet it is.
But anyway, that's the basics of what all was involved!