Rigged Riddle

"Not fair! not fair! It isn't fair, my precious, is it, to ask us what it's got in it's nassty little pocketsess?"

- Gollum

A “riddle” for which the person answering can not reasonably know the answer, as it depends on information only the asker should know. Obviously the person asking the riddle tends to win.

Literature

 * In The Hobbit, Bilbo asked Gollum “What have I got in my pocket?” Understandably, Gollum asserts that this riddle isn't fair. Funny thing is Bilbo was talking to himself when he said this, but Gollum interpreted it as part of their riddle game and it is only after Gollum protested that Bilbo deliberately used it as the riddle.

Live-Action TV

 * On both the radio and TV versions of You Bet Your Life, Groucho Marx frequently asked contestants "Who is buried in Grant's tomb?" The correct answer is "nobody", since the late President Grant and his wife are interred in sarcophogi above ground level.  Unlike the usual Rigged Riddle, this one depended as much on an automatic but faulty assumption on the part of the contestant (that the deceased are always buried) as on knowledge not available to them.  That Marx could keep asking that question for the 14 years he hosted the show testifies to the strength of that assumption, even when the question and its answer became a cultural meme.

Oral Tradition, Folklore, Myths, Religion, and Legends
"What did Odin speak into Baldr’s ear before he was placed on the pyre?"
 * Odin did this a couple of times in Norse Mythology. On both occasions, he used the same question


 * In Hervarar saga ok Heiðreks (The Saga of Hervör and Heidrek) One time while Odin was disguised asked King Heidrek numerous riddles. In this contest, Odin was the only one asking riddles.
 * Odin asked this with Vafþrúðnir (mighty weaver) in the poem Vafþrúðnismál. In this contest Vafþrúðnir and Odin asked each other riddles.
 * In The Bible, one time Samson came across a lion corpse with a beehive filled with honey inside and used that as the basis of the riddle.
 * What is Rumplestiltskin’s name?

Radio

 * As noted above in Live-Action TV, Groucho Marx frequently asked contestants on the radio version of You Bet Your Life "Who is buried in Grant's tomb?"