Surprising though it may be, many wikimedians enjoy... working on Wikimedia projects. They sometimes go out to the pub with each other and have fun in real life. But let us not confuse "enjoyment" with "fun". Writing WP articles, uploading photos to Commons, transcribing wikisource articles, working with newbies anywhere... these are not "fun" and are not supposed to be "fun". Because we all believe in the greater mission of free-knowledge these activities are "enjoyable".
If you want to see *funny* things on [English] Wikipedia, go to http://en.wikipedia.org/wiki/Project:Bad_Jokes_and_Other_Deleted_Nonsense or https://en.wikipedia.org/wiki/Wikipedia:Unusual_articles
For everything else - there's always http://zombo.com/ Anyone can have fun there for as long as they wish.