Ranma to Ranma? Gokai ga tomaranai - S1-E4
Other mistake: Nabiki pours a bucket of cold water and then a teapot of hot water over Ranma as he sleeps, but he does not wake up. Some heavy sleeper. Also, all of this somehow leaves just a warm patch under her groin area, leading to the obvious misunderstanding. But her pillow and other half of the futon should be drenched too. (00:09:05)