Set somewhere in season 6.
"Were you aware that Halle Berry's stunt double in the movie Catwoman was in fact a man?"
Dr Saroyan turned to him, wearing her I'm-trying-not-to-get-offended look that she seemed to wear a lot. At least, around him she did. "I could take that one of two ways: either you're implying I look like Halle Berry or you're implying I look like a man." Vincent frowned; he was sure that wasn't what he was trying to imply. Dr Saroyan smiled tightly. "For your sake, let's assume the former. What have you come as?"
"Isn't it obvious? Sherlock Holmes. Legendary sleuth." He flicked the brim of his deer-stalker cap and raised his pipe, taking an imaginary puff of it. "Did you know that 'Sherlock' literally means light-haired, yet all of the main characters are dark-haired?"
Her smile was either amused or a little exasperated. Sometimes it was hard to tell the difference. "I did not know, actually." Vincent grinned cheerily.
They stood in silence for a short while, until Daisy bounced through the door wearing what looked like a homemade butterfly costume, papier-mâchéd to the nines. "I better go, make sure Daisy doesn't monopolise the fruit punch," Dr Saroyan explained, rolling her eyes, and then leaving with swish of her cat tail.
"Dr Saroyan!" Vincent called out, a moment too late. She was already out of earshot.
Vincent sighed, taking his hat off and scrunching it up in his hands. "I think you look better than Halle Berry," he said to no one. "A lot better, in fact. Much, much better than Halle Berry."
When he looked up, Booth (dressed as a gangster) was staring at him from where he stood next to Dr Brennan (dressed as Wonder Woman). He looked empathetic. Hang in there, he mouthed. Vincent nodded slowly and raised his pipe in acknowledgement, then made his way to the door. He didn't feel much like partying any more.