Here are a couple of my favorite examples of gullible people (true stories).

Back in the days of the Mattel Cabbage Patch Kid craze it was usually
very hard to get one for the kiddies. A radio station (I dont know where)
announced that Mattel was going to get Cabbage Patch Kids out to the people
of this particular city. The plan was that they had to go to the football
field of the local university and wait. An airplane would fly overhead and
the dolls would be dropped onto the field. People were supposed to hold
their credit cards up so that a photographer with a telephoto lens in the
airplane could get the credit card numbers and charge the price of the
dolls to the recipients accounts.

People actually showed up, waving American Express cards in the breeze.

Another radio station prank took place on April Fools Day. They
announced that the phone company would be cleaning the dirt out of the
phone lines that afternoon. They do this, it seems, by blowing air into the
wires in the switching station. The problem is that the dirt comes out of
the earpiece and mouthpiece of the telephone, and could dirty the rugs or
furniture in your house. Consequently, the phone company asks that the good
citizens please get plastic baggies and put them over the handsets of the
telephones to protect their belongings.

Stores reported a run on plastic bags, and the phone company made the
radio station retract the original claim.

Ive always felt that the retraction should have been handled this way:
The phone company would like us to tell you that our earlier message
concerning the blowing of dirt out of the phone lines was incorrect. The
phone company does not, repeat NOT, blow into the telephone wires to clean
out the dirt. Anybody with any understanding of the way the system operates
would know that they suck the dirt out.

Alas, the retraction was serious and factual. Whats this world coming
to anyway?