In the "tag" at the end, Artie and Jim get different hair styles and Artie suddenly loses several pounds. The episode was filmed in May of 1968 but held back to February 1969 until after Ross Martin recovered from his heart attack. The tag was filmed later after Martin lost weight from his illness.
Pike's disguise: Baron Klaus Esterhazen of Estavia
Gadgets: exploding pouch, sleeve derringer w/dart and wire, windup noisemaker
When Jeremy drops the phonograph, the ground beneath it sags when the box strikes the "dirt." When Jeremy picks it up and steps on the same spot, the sagging is even more noticeable.
Professor Montague's code-breaking efforts don't make sense. He only has half of the song title on the chalkboard, with no indication that he's worked on the second half of the title.
Disguises: none (Artie or the other substitute back-up disguise experts aren't in this episode)
Gadgets: wind-up gunshot noisemaker
Three heavies jump Jim at the mortuary. They all manage to escape. However, in the two subsequent scenes involving the heavies (with Ned at the Nolan mausoleum, and later at the big showdown in the mausoleum), only two heavies appear. The third one's absence is never explained.
Gadgets: fake explosive powder, plastic explosive, boot-tip knife
Due to the insurance issues after Robert Conrad injured himself last season, a stuntman is used when Jim drops on Chaveros. However, the stuntman looks almost nothing like Robert Conrad.
The wagon driver at the end is clearly not William Schallert.
Harper's disguise: Ambassador Ramirez, Prof. Wolfgang Kralle
Occularis hides the raven in Frank's hotel room. However, Occularis doesn't know that Frank was disguised as Mayor Snead. Occularis would have hidden the raven in Snead's house, not Frank's hotel room.
In the establishing shot of the city, the title card says "State Capitol." Capital refers to a city that is the state capital. Capitol refers to a specific building. So it is State Capital, or State Capitol Building, but never State Capitol.
In the establishing shot of the Wolfville Jail, the poster of the Brass Gang is black and white and on a brick wall. Later when Jim leaves the jail, the poster is in color and on a corkboard.
Harper's disguises: Mayor Hiram Snead
Disguises: Mexican guitar player, Juan Ramirez
Gadgets: Fake rattlesnake tail, wind-up explosives, boot heel with plastic explosive
During Jim's fight with Cortez's thugs in the main hall, at one point they slide him along a table and onto the ground. One thug keeps fighting, but the thug on the left casually turns around and strolls away. The thug on the right settles down and starts tucking his tunic back in.
During Jim's fight in the main hall, hot wax is supposedly dropping down the candles in the candelabra. However, the table takes several hits and the candelabra shakes noticeably, but the wax stays in place.