Not everything about Scrum has to be serious. In fact, because of the Agile emphasis on 'Individuals and interactions over processes and tools,' I've personally found this mindset often fosters more 'fun' work environments than anything traditional project management can do. Aside from this natural Agile tendency towards a less dour situation, I also like to inject a little levity into the process wherever seems appropriate. One way I do this is with Sprint mascots.
Every scrum team I work with through an Agile transformation chooses a genre when we plan our first sprint. It can be absolutely anything, from a movie franchise to celestial bodies, and all points in between. When a team completes planning a sprint, I ask them if they have a mascot from whatever they have chose that they would like to use. This can work in different ways.
One team I've worked with uses Star Wars, and so each sprint is named after a character from that franchise. There's a team member with an encyclopedic knowledge of the Star Wars universe, and he whimsically describes how this sprint that's planned reminds him of some particular (often but not always obscure) character. The team approves, and off they go. Another team decided to use cowboys and Westerns in general, opening up myriad possibilities from the worlds of TV and cinema, including animated characters like Yosemite Sam and historical figures like Billy the Kidd. With them there's a bit more discussion and no one designated 'namer.' It works out.
When possible, I play along with the team's choice.For example, there's a team I worked with a couple of years ago that decided to name their sprints after breakfast cereals. The first day of each new sprint I brought in a box of whatever type of cereal the team had chosen, and it was available for anyone who wanted some. During the two weeks of the sprint it sat on a shelf over the area where the team worked, like a flag flying.
What does this actually accomplish? I'm certain it doesn't do anything either way for velocity, but it certainly gives a small morale boost, and the teams I work with clearly enjoy it. Why make work dreary or treat people (aka 'resources) like machines? There's nothing wrong with a little fun, especially when Agile is involved.