"You can't deny laughter; when it comes, it plops down in your favourite chair and stays as long as it wants."[1]
Simple: You can't say "no" to laughter. When it comes, it sits down suddenly in the chair that you always like to sit in. It stays for as long a time as it wants.
References
↑Angier, Michael E.; Sarah Pond (2004). 101 Best Ways to Get Ahead. Success Networks. ISBN 0970417535.
