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"Doctor Know-all" (German: Doktor Allwissend) is a German fairy tale collected by the Brothers Grimm, tale number 98 in Grimm's Fairy Tales. It is Aarne-Thompson type 1641 about being in the right place at the right time. Another tale of this type is Almondseed and Almondella.
A peasant named Crabbe saw how well a doctor ate and asked him how to become one. The doctor told him to buy an ABC book with a rooster up front, sell his oxen and cart to buy doctor's equipment and clothing, and advertise himself as "Doctor Know-all." Crabbe takes this advice serious and soon becomes a doctor under this name.
Shortly after he set himself up, a nobleman visited him and asked to find stolen money. Crabbe insists that his wife should come along. At the nobleman's home Crabbe and his wife are invited for dinner. When they sat to eat, Crabbe nudged his wife at each course, saying "That's one," "That's two," and "That's three" — meaning three courses. However, the servants who brought the dishes and who'd actually stolen the money thought he was identifying them. The fourth servant then brought the final meal under a covered tray. The lord asked the doctor to show his all-knowing skill and guess what was underneath the tray. Crabbe, who had no idea, pitied himself and cried: "Ah, poor Crabbe!" As it happens the meal was indeed a plate full of crabs.
All four servants were now in complete panic. They asked Crabbe to speak to him confidently and confessed their crime. If he would not denounce them they would willingly restore the money and give him part of the finders' reward. Crabbe agreed and was shown where the loot was hidden. He then went back to the nobleman, sat down to the table and pretended to look for the answer in his ABC book. Meanwhile, a fifth servant was hiding inside a stove to listen if Doctor Know-all still knew more. When Crabbe tried to look up the answer he said: "I know you are there, so you better show yourself!" The servant inside the stove thought Crabbe meant him and jumped out the stove. Then Crabbe revealed where the money was and received a lot of money both from the nobleman as well as from the frightened servants, becoming a wealthy and renowned man.