Jim sends Spock crude sexual drawings for shits and giggles in their free time (or maybe during a really boring conference or something)

Spock sends back altered anatomically correct versions.

"Jim, that position is not physically possible."

"Jim, my penis is not that large."

"Jim, I do not wear that particular expression during intercourse. I never wear that particular expression."

Eventually, just arrows pointing to various errors labelled “No, Jim.” “JIM, NO.”