What goes up but never comes down?

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

Spot 5 differences in two Christmas tree below:

If an electric train is travelling south, then which way is the smoke going?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

What do you call a fish without an eye?

Identify the hidden meaning behind this picture?

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?