Isabelle: We could get into trouble.
Hugo Cabret: That's how you know it's an adventure.
There is a scene where Hugo is on the station and sees a key down on the tracks. There are two seperate shots of the key and both times it is buried in the stones next to a sleeper. Then Hugo jumps down onto the tracks to pick it up and its now quite sat on the middle of the sleeper when he picks it up.
Shortly after Hugo drops a piece of metal from the suspending clock to the ground of the train station, the Station Inspector, assuming that Claude dropped it, loudly asks him if he is 'drunk, inebriated, shikker, etc.' The work shikker is from the Hebrew word shikkor for 'drunk'. Shikker actually means drunkard.