Sharing with one person is still better than a cube or open plan.
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.