Answer:
What Has 4 I's but cant see? Mississippi!
What gets dryer as its getting wet? a towel!
Ask what the person's name is, ask what the color of the sky is, and ask what the opposite of down is. You'll end up with, [the persons name] blew up.
[The last one is not really a riddle, but it's fun!]
Also there's more hard ones like:
1. A farmer has a bag of grain, a chicken, and a fox. The farmer must travel to the other side of the river in his boat but the boat can only hold the farmer and one other item. The Chicken and Grain cant be together. The fox and chicken cant be together how does he cross the river?
Answer
You first take the chicken to the river in the boat leaving the fox and the grain, you leave the chicken at the other side, then you go back and take grain to the other side of the river also, but when you leave to get the fox, you bring the chicken back to where it first was, then the farmer picks up the fox, and leave the chicken behind and brings him to the other side of the river, and lastly he goes back to the original side of the river and brings the chicken over to the fox and the grain.
2. A man and a dog were going down the street. The man rode, yet walked. What was the dog's name?
Answer
Yet.
3. A man and his son were in a car accident. The man died on the way to the hospital, but the boy was rushed into surgery. The surgeon said "I can't operate, for that's my son!" How is this possible?
Answer
The surgeon is his mother