Other mistake: In this episode it's shown that Charlie can hear Alan's adventures in the bedroom. However, Charlie's room is up 2 flights of stairs and Alan's is down a hallway away from the stairs. (00:02:45)Ssiscool
Continuity mistake: Charlie tells the psychiatrist that apart from being constipated everything is fine and the house is paid off. However later on when Walden moves in, it is said there are three mortgages on the house which Alan can't afford (which is why Walden moves in in the first place).
Factual error: Alan and Lyndsey are playing scrabble. Alan is shown laying tiles down horizontally, and claims that he is using the "Z" on a triple letter score, and the "I" on a double word score, changing "it" to "ziti". This is impossible on a normal Scrabble board - those multiplier squares are all offset from each other except one row, and then they're five squares apart.
Continuity mistake: As Alan runs away screaming about betrayal, Berta begins to pour Charlie a cup of coffee. Charlie's first two or three fingers are hooked through the handle of the cup. The shot changes and Berta is still pouring but now Charlie's index finger is alongside the rim of the cup.Guy