I saw a vid clip, where someone was asking people to apply for something, and one of the questions was “how much do you weigh”, but what the person did not know was a) it was being filmed and b) the rubber mat in front of the booth (where the apps were being filled out) was really a scale pad.
Visible to the studio audience was the vid feed with sound (so they can hear what weight is being said) and a display showing the actual weight.
Its amazing how few people know their true weight.