Explanation:
A man lives on the twelfth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator -- or if it was raining that day -- he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up two flights of stairs to his apartment.
Solution:
The man is a dwarf. He can't reach the upper elevator buttons, but he can ask people to push them for him. He can also push them with his umbrella.
Explanation:
A man walks into a bar and asks for a drink. The bartender pulls out a gun and points it at him. The man says, "Thank you," and walks out.
Solution:
The man has hiccups; the bartender scares them away by pulling a gun.