Riddle: One day, down at the South Pole, five penguins and twice as many polar bears got onto a train. The train was headed to another station that was 15 minutes away from where it was initially. What is wrong with this story?
Answer: Polar bears live at the North Pole, while penguins live at the South Pole. They can't coexist at the same Pole.
Riddle: A green apple costs $1, a red apple costs $2, and a blue apple costs $3. If you have $3, but only two bills, what apples can you buy?
Answer: There are two solutions; you can either buy one green apple and one red apple using a $1 and a $2 (yes, $2 bills are a thing), or you can buy three green apples using the same two bills. You could have bought one blue apple using those bills, but blue apples don't exist!
Answer: The ambiguity of this riddle means that the answer could be either two or three. But the real answer is three because you have to follow the order of operations (half of two is one, and one plus two is three).
Riddle: Charles called his wife to tell him that he would be home by 7:00. But when he arrived home three minutes past 7:00, his wife was furious! Why was she so mad?
Answer: Charles' wife expected him to arrive by 7:00PM, but he arrived at 7:03AM the next morning. Oh, the classic "I forgot about ante meridiem and post meridiem".
Riddle: Ally and Gwen were told to do house chores on a rainy day. Ally chose to hang the laundry outside to dry, while Gwen vacuum-cleaned the bedrooms. Who is more stupid?
Answer: Ally is more stupid because it was raining all day, and there wouldn't be any need to hang laundry outside.
Riddle: Oliver and Brittany are siblings. They were born in the winter and summer. If Brittany was not born in the winter, then who was born in the summer?
Answer: If Brittany was not born in the winter, then she was born in the summer. Therefore, it's Brittany.