Obviously there's only water in Mary and Trent's coffee mugs.
The staircase in "Up the Stairs" designates the Man Cave as Level 1 -- but this episode reveals the Man Cave as the fifth Man Cave out of ten originally built. Since the elevator buttons number the Man Caves in ascending order, the stairway should have started at "Level Five" -- but if it had, it would have seemed like a mistake.
Piper's ability to avoid arrest hinges on her cooking, which has been established many times over as far from digestible. Jake should know this but doesn't flinch for an instant.