The level of drink in Jack's glass changes between shots in the opening sequence.
Frank has two phone applications, one that produces a high pitched sound that only younger people can hear, another that produces a low sound that only people over 40 can hear. The first makes sense, given that as people get older they lose the ability to hear higher frequencies. The second doesn't, as older people do not gain the ability to hear low frequencies as their ability to hear higher frequencies diminishes.
At the end of the episode when Lutz is wildly dancing in the back light, he jerks his martini glass around so intensely that at times it is upside down. The liquid inside falls to the brim but doesn't spill, revealing it is a stunt glass with the liquid actually contained within the frame of the cup.