A Practical joker (n.) is a person in good humor who puts others in bad humor.
A Practical joker (n.) is a person in good humor whose humor is seldom good.
A Practical joker (n.) finds nothing funny in a joke unless it's at someone else's expense.
A Practical joker (n.) has a sense of humor that's made up of little sense and less humor.
A Practical joker (n.) never grows into his second childhood because he never grows out of his first.
The Practical joker (n.) shakes your hand one minute, and pulls your leg the next.
A Practical joker (n.) spends half his time trying to get others into trouble, and the other half trying to get himself out of it.