All of the human kids are extremely good dancers.
John knows all of the rave dances, all of them. Rose knows classical ballet. Jade was taught the Charleston by her grandpa. Dave's special is breakdancing.

Dave is heteroflexible.

Dave is secretly a huge Doctor Who fan and no one knows this except John because Dave recommended it to him and went into a long explanation of the show.

Dave is an art prodigy, he has to put in a lot of work to make SBaHJ look as bad as it is.

When Dave and Nepeta first met, Nepeta opened up her trench coat to Dave saying "Check out THESE kittens!"... she literally strapped kittens to the inside of her coat.

John speaks French fluently.