The actress told the Futon Critic that the episode, which will guest star True Blood's Kevin Alejandro, will be "fun".
"There's a lot of humour [and] really crazy characters," she promised. "It's [set] in a bowling alley [and] we're undercover at a bowling league. [Booth and Brennan are] ridiculously conspicuous, but undercover!"
She added: "[But] there's some deep, big things that happen as well. I recommend that everybody watches the entire episode [because] you could miss something."
Deschanel also revealed that the show's writers are still undecided on how to deal with her real-life pregnancy.
"They know how I feel about it all and how I feel about how they want to treat my pregnancy," she said. "But it's ultimately their decision how they handle it in the show."
She previously suggested that it was "unlikely" that her character Brennan would also fall pregnant.
Bones airs on Thursdays at 9/8c on Fox. The sixth season finale airs on May 19.
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