This is an experiment...

Martin T. Orne, "On the Social Psychology of the Psychological Experiment," American Psychologist 17 (Nov. 1962): 776-783.

[T]he subject agrees to tolerate a considerable degree of discomfort, boredom, or actual pain, if required to do so by the experimenter. Just about any request which could conceivably be asked of the subject by a reputable investigator is legitimized by the quasi-magical phrase, "This is an experiment" . . . .

A number of casual acquaintances were asked whether they would do the experimenter a favor; on their acquiescence, they were asked to perform five-push-ups. Their response tended to be amazement, incredulity and the question "Why?" Another similar group of individuals were asked whether they would take part in an experiment of brief duration. When they agreed to do so, they too were asked to perform five push-ups. Their typical response was "Where?"

NOTE TO SELF: TRY THIS AT THE BAR NEXT TIME YOU ARE THERE..."This is an experiment...buy a drink for me..."

Stolen from this guy.