They were forced to take psychotropic medication (which they sneakily spit out) and were eventually discharged with a diagnosis of paranoid schizophrenia in remission.
One of the subjects started dreaming of cannibalism and, when confronted by the lead scientist about sneakily buying food during an authorized excursion, threatened to kill him.
Sidekicks are one of the most common and direct ways to do this: they can supply sneakily perceptive commentary on the main action, often while simultaneously serving as blundering, hapless punchlines.
The other day I was sneakily eating a piece of chocolate in the kitchen and Dan, my husband, walked into the kitchen and said, " Did you eat the last piece of chocolate? "