The shirt worn by the 'changeling' in the opening scene is missing the stitching on the left breast.
Walter says that Sumerian is not his favourite ancient language, and he prefers Yiddish. Yiddish is far from being ancient, as it emerged in the Middle Ages as the conglomerate of Hebrew and High German, later incorporating some Polish and Russian vocabulary. Walter probably meant Hebrew that is indeed an ancient language.
When Lincoln, Peter and Olivia go to Daniel Hicks house the electric is off, but when Peter opens the refrigerator, the inside light is on.
When Lincoln knocks on Hicks' door, we hear 5 knocks, but Lincoln only physically knocks 3 times.