I have been working on a Scrum team as a team member for 10 sprints (about 5 months), and I have found that time for fun is very important. As we already know, Agile/Scrum works differently than traditional Waterfall. The Scrum team needs more member initiative and plenty of positive attitude. Team members use their own initiative to take on tasks, and the team members tend to be happier and dedicate more effort. I commonly hear, "I love this Scrum team, I feel happy on the team, I like to work here."
I'd like to add, however, that play
in work can also be an element that helps the team work happily and well. In our retrospective meetings, we have found a way to make the work more fun. Since it's summer, it is very hot, so we make the Friday our Watermelon Day. The ScrumMaster buys a watermelon on Friday, and the watermelon's size relates to the story points we have accomplished this week -- S, M, L, or XL.
It makes for a wonderful Friday!