Yeast and Mushrooms

I love conversations with Greysen where he exhibits that he really is still a 4 year old.  Greysen asked me, out of the blue one day, if I knew what a "funny guy" was.  I told him that of course I knew it was him.  He protested.  "NOOOO, a 'funny guy.'"  Understanding at this point that he meant something other than what he was asking, I looked at him curiously.  He said, "....like yeast or mushrooms."  It dawned on me, "Ooooh, you mean fungi?" 

I tried really hard not to laugh.