Getting a job in a restaurant no matter what position (all job expectations) will include doing things that are never listed on any job description. There is no way you could ever really prepare yourself for some of the things you might be asked to do. It has seemed to me that the less corporate your place of employment, the more likely you'll be asked to do something just crazy. Mom and pop places are notorious for this kind of behavior for a few reasons including no actual job descriptions and no one else around to do the work.
Some of the things I can think of that I've been asked to do includes some tile work (cleaning grout, laying grout, ripping up tile, etc.), plumbing work (from plunging toilets to changing pipes on a three compartment sink), computer systems (setting up POS systems to wiring screens), and all other sorts of general labor like filling in pot holes in the parking lot, laying gravel, pulling weeds, painting signs, setting up racks, putting up shelves, etc.
This kind of thing would never happen at an accounting office or law firm. Can you imagine a lawyer filling in pot holes outside their office? Ha! When you are working in a restaurant you really need to be a jack-of-all-trades. I can only imagine some of the things some people are asked to do.