Continuity mistake: Midway through this episode as West is ascending the outside wooden steps to Moriarty's office, his shirt has a vertical rip in his upper left chest area. Once West goes inside, that rip is no longer there but is replaced by a much larger vertical rip (much lower from his waist up to his chest). This larger rip is seen throughout this scene. When West leaves Moriarty's office, the larger rip is no longer there and the original smaller higher rip re-appears. In the following scene when West is changing his shirt, the smaller upper rip has been replaced by the much larger lower vertical rip.
Continuity mistake: As the boxing match moves from inside to outdoors, West's shirt is drenched on the back, as well as around the collar and top front of the shirt. Outdoors, those areas are dry. When the fight moves by the water, West shirt is torn on his front left (length from the 2nd to 4th buttons). At the end of that scene, that tear no longer shows, but a new one appears much higher (length from 1st to 2nd buttons) and is closer to his arm in the upper left chest area.
Continuity mistake: Before the title appears for this episode, in a long screen shot, West is knocked out face-up with both arms extended above his head; only his left elbow is touching the knocked out bad guy next to him. The next immediate close-up shot of West shows West with only his right arm extended above his head and his body is much closer next to the bad guy. As the title appears, West is face-down resting on his right arm when he starts to regain consciousness.
Factual error: Artemus opens a cabinet to reveal a map of the United States where he and West are keeping track of the alphabetical murders. The map is far out of date for the Grant administration, with what became the state of West Virginia during the Civil War still part of Virginia, and missing entirely the states of Nevada, Oregon, Kansas, Nebraska, and Minnesota-all of which were part of the union before President Grant took office. (00:04:45 - 00:06:30)