At one point Don takes a picture of Midge and Roy. Later when Don reveals the photo, the angle of their bodies to the camera and their distance from each other don't match the shot.
In a flashback scene the hobo shows young Don (Dick) some hobo "codes". He
draws one that looks like two W's and says "That means watch out for the nasty
dog." The camera cuts to his face as he speaks, then back to a different set of W's as he continues.
When Midge puts on Miles Davis' Sketches of Spain, the record on the turntable has the red Columbia label used after 1961, not the "six-eye" label which was used in 1960, when this episode is set.