easy

How can a pants pocket be empty and still have something in it?
Common Wrong Answers
“It has a small object inside.”
While a small object could technically be inside the pocket, the riddle specifically implies that the pocket is empty, so this answer contradicts that premise.
“It's turned inside out.”
If a pocket is turned inside out, it would not be considered empty; rather, it would be showing its contents, which is not the intended meaning of the riddle.
“It is a magical pocket.”
While a magical pocket could theoretically have something in it without being full, the riddle is meant to be a play on words regarding a physical hole, not a fantastical concept.