The workplace is not always conducive for showing off our unmasked personalities. An air of professionalism is expected, and rightly so. But if the only interaction you have with coworkers is through the filter of business, meaningful connections will be hard to make.
I never liked group projects or team building activities. I did not like depending on others for success, and more often than not I would be stuck with the "bill" (namely, all the work). But as cheesy as group activities can be, they allow facade-less interaction.
No matter how "stiff" a person may be, outright silliness can help people lower their guards. When you choose to do slightly embarrassing things, others will feel empowered as well. And once a safe environment is established without the prerequisite of professionalism, people can truly connect with one another.