Ever since I saw some movie exploring Lucid Dreaming I've had a few instances where I was able to recognize and take control of the dream. A couple of times I was having a nightmare that I dispelled, but there was that one time. It was a harmless dream where I was talking with a grown-up version of a friend I had not seen or heard from since 3rd grade about an argument we had way back then of who was stronger but somehow I couldn't speak for myself. It was at this point I was aware of the dream and was able to take control by responding that I was no weakling with examples of physical prowess from the past... then I remembered tearing the muscles of my back in a weight-lifting accident. I woke up in screaming pain that lasted for a few seconds after I was fully alert. The thought struck me while I was trembling in bed with the flood of adrenaline that the brain stores quite a bit of our experiences and that perhaps full recall may be more harmful than good. Take this as a cautionary tale or a grain of salt, your choice.
Doc is experimenting with wish fulfillment... and he wants a drink with an umbrella. Really? "Hey, wonder what I can do? Let's see. I think I'll try to get - a fancy drink in a tankard!" The big guy just got knocked into La La Land over his accusation that Pirta messed with his coffee. The least I would've expected was for the first wish to be God's own ambrosia of coffee brews delivered personally by the man. I mean, Doc was craving coffee and he knew what it was supposed to taste/feel like so why not scratch the itch?