Flora Whiff (Bebe Neuwirth), the famous expert on smell—whose "nose knows"—comes to school to judge the First Annual Smell Search. Ms. Frizzle's class creates a unique smell which is bound to take first prize, but Arnold's cousin, Janet, determined to win by herself, evilly corrupts their smell to a stench that even a skunk would hate. The kids discover the secret to what makes things smell...now they have to make sure their creation will not make a big stink. Michael makes a cameo, since he did not appear with Ms. Frizzle and her class.  There is a big mistake in which Ralphie is talking using the voice of Arnold right after they get out of the trash.