Ward Fowler draws a chalk circle on the back of Columbo's raincoat. Quite a bit earlier, when beside the "Jaws" pool, Columbo could be seen with that chalk circle already on his back.
Before the in-studio patio setting, a blonde in a gold quilt-patterned dress passes Columbo left to right. When the camera cuts to a closer shot of Columbo and Ward, the blonde is seen in conversation before breaking off and passing by Columbo, again, left to right. (Other background extras also fall among errors in continuity, but none more prominently.)
At the "Jaws" pool, Columbo's cigar travels between either hand to mouth without transitions.
Before moving away to fetch a piece of chalk, Columbo takes his cigar in his right hand, but as he takes the chalk (seen through a different camera), he holds his cigar in his left hand.
Shortly after Colombo meets Ward Fowler in the studio, Ward pours himself and Colombo a cup of coffee. Columbo sets his cup on top of a ladder and asks Ward a question. As Sid walks up, Columbo is holding another cup of coffee while his cup of coffee is still on top of the ladder, and Ward's cup is gone.
Ward Fowler's video recorder takes one second to rewind an hour and thirty-five minutes of a taped broadcast. No cassette machine rewinds that much footage that fast.
The baseball footage shows the Baltimore Orioles of the American League at home in Memorial Stadium (during the daytime) but the announcer refers to one team as "Los Angeles". That would make the visitors the Los Angeles Dodgers of the National League who would not play a regular season game at Baltimore until more than twenty years later.
The baseball announcer refers to one team as "Los Angeles" and mentions their game the previous week in Kansas City. At that time, the teams could only be the Los Angeles Dodgers of the National League and the Kansas City Royals of the American League, but they would not play a regular season game against each other until more than twenty years later.
The cash Ward pulls from Clare's wallet during the "robbery" is clearly not real money.
William Shatner's toupee is plainly visible at the end. His forehead moves but the hair does not.
As Fowler approaches the video recorder after the crime, to stop and rewind the tape, the baseball announcer is saying that a new pitcher is coming into the game from the bullpen. However, the live TV picture is of a shortstop fielding a ground ball. This could not happen during a pitching change.
Ward and Mark watch a televised Dodgers baseball game. Though it's night, the live game occurs on a bright sunny day.
When Columbo is in Sid's office and the latter fixes himself a drink, the shadow of a microphone can be seen coming and going in the upper left corner.
When Columbo first meets Ward Fowler at the studio, Mark comes up to them both with a mug of soup in his hand. Mark tries to calm Ward down, but confuses the character names as he says to Ward, "Take it easy, Mark."