Here is another scary example (known to be true, by way of two of the participants): a (then) young postdoc approached R. Langlands and A. Borel (this was in the late seventies), in the IAS tea room, and the following conversation ensued:
Postdoc: Do you guys know anything about automorphic forms?
B&L: Maybe
Postdoc: Well, can I ask a stupid question?
B&L: Well, you have already asked one.
