Or, depending on the person, much much worse.

In the late 90s I shrared an office with a guy, and he was great and really nice - we both liked to work with the lights out...

But he had a very peculiar look to his face, like a charicature. So when we would spin round in our chairs to discuss something, he'd be talking to me about something very serious about work and I would start to giggle.

He would say "what why are you laughing?" And I would have to say things like "in sorry something you said just reminded my of something funny"

I had a really hard time maintaining a straight face around him - I felt so bad about it.