I have a funny story....we twice had the misfortune of spilling a beverage (one water, one juice) on the bed. I called to request new sheets and pulled the sheets so the staff would know which one to change. (I also left a note and an extra tip both times.)
Sure enough, when the bedding was replaced, there was a plastic sheet under the regular sheet; I gather that the staff had assumed the wetness was from pee. (or maybe that if we spilled once we'd do it again?)
The two spillings happened on two different trips, and neither time did I think to inform the staff that the liquid in question was just a beverage. I dont know why. It wasn't until I discovered the plastic sheet the second time that I recalled the first. They were on different trips to WDW, and at very different resorts.
If you know this is an issue, it may be wise to inform the staff in advance. I am sure it happens all the time, and indeed WDW may employ protective matress pads, but when it's an issue - they most certainly
add a plastic sheet!
Further - good advice for all - if you happen to spill a beverage on the bed and need new sheets - be sure to let the staff know that
liquid is a beverage- or you'll end up with plastic sheet under the regular one


(plastic sheets are really uncomfortable in warm weather)