During the introduction, after Newkirk punches Williams and they end up on the floor, Hogan comes out and Newkirk and Williams are pulled apart. Williams' hands are empty. There is a cut to show the whole group and the door to the barracks, which opens, and Schultz and Klink come in. Hogan starts counting to make it appear that the prisoners are dancing. Now Williams has a handful of money, which he could not have picked up during the cut to the wide view.
During the introduction, Newkirk accuses Williams of cheating at cards. Newkirk causes Williams to show the card at the bottom of the deck. The way Williams is holding the cards is as a stack of cards, with the faces toward his palm (he's the dealer). There is a cut to show the view from over Newkirk's left shoulder as he goes to punch Williams. Williams is now holding the deck fanned out, with the card faces away from his palm, as if he is playing a hand of some kind of card game (rather than poker). It also appears that there are significantly fewer cards in Williams' hand than there were before the view changed.
When the door to the cell in the cooler is blown the stick of "dynamite" falls to the ground with the fuse still burning after the explosion.
When Schultz captures Williams outside the camp, as he is walking back toward the camp, he has white marks on the back of his right arm - probably from the fake snow on the trees he was walking through.
When Williams first starts talking to Klink, LeBeau indicates that they used Williams on one job. Later, when Carter tells Hogan what Williams teased Klink with, LeBeau indicates that was one of the jobs they used Williams on - implying they used him on more than one job.