I walked into a Blimpie's with a buy-one-get-one-free coupon for a sandwich. I handed it to the girl and she looked over at a little chalkboard that said "buy one-get one free". "They're already buy-one-get-one-free", she said, "so I guess they're both free." She handed me my free sandwiches and I walked out the door.

They walk among us (and many work retail).
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A friend of mine bought a new fridge for his house. To get rid of his old fridge, he put it in his front yard and hung a sign on it saying: "Free to good home. You want it, you take it." For three days the fridge sat there without even one person looking twice at it. My friend decided that people were too untrusting of this deal. It looked too good to be true, so he changed the sign to read: "Fridge for sale $50."

The next day someone stole it.
They walk among us.
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One day I was walking down the beach with some friends when one of them shouted, "Look at that dead bird!" Someone looked up at the sky and said, "Where?"

They Walk among us!
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While looking at a house, my brother asked the real estate agent which direction was north because, he explained, he didn't want the sun waking him up every morning. She asked, "Does the sun rise in the north?" When my brother explained that the sun rises in the east, and has for sometime, she shook her head and said, "Oh, I don't keep up with that stuff."
They Walk Among Us!!
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I used to work in technical support for a 24/7 call center. One day I got a call from an individual who asked what hours the call center was open. I told him, "The number you dialed is open 24 hours a day, 7 days a week." He responded, "Is that Eastern or Pacific time?" Wanting to end the call quickly, I said, "Uh, Pacific."
They Walk Among Us!
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My colleague and I were eating our lunch in our cafeteria, when we overheard one of the administrative assistants talking about the sunburn she got on her weekend drive to the shore. She drove down in a convertible, but "didn't think she'd get sunburned because the car was moving."
They Walk Among Us!
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My sister has a lifesaving tool in her car designed to cut through a seat belt if she gets trapped. She keeps it in the trunk.
They Walk Among Us!
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My friends and I were on a beer run and noticed that the cases were discounted 10%. Since it was a big party, we bought 2 cases. The cashier multiplied 2 times 10% and gave us a 20% discount.
They Walk Among Us!
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I couldn't find my luggage at the airport baggage area, so I went to the lost luggage office and told the woman there that my bags never showed up. She smiled and told me not to worry because she was a trained professional and I was in good hands. "Now," she asked me, "has your plane arrived yet?"
They Walk Among Us!
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While working at a pizza parlor I observed a man ordering a small pizza to go. He appeared to be alone and the cook asked him if he would like it cut into 4 pieces or 6. He thought about it for some time before responding. "Just cut it into 4 pieces; I don't think I'm hungry enough to eat 6 pieces."
Yep, They Walk Among Us!
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AND they reproduce!