An Odd Story - Part I

This is something my elder, Don, was telling me about. There are a couple of different pieces to the puzzle of this situation, which I'll make in different posts.

Don had a friend who was in the hospital, so he went to visit him. Don always likes to try and share jokes or funny stories, so while this guy sat in his hospital bed, Don told him a joke about a large cat that Don thought was pretty funny. Upon telling the joke about the large cat, the other people present laughed except for the man in the bed (we'll call him 'Bob'). Bob responded by turning slightly pale and pulling his covers up tight against him, similar to a child hiding from the boogie-man. Later, a friend present invited Don out to the hall to tell him a story.