During the scene of Theodore and Amos crossing above the alleyway to the bank, Don Knotts was genuinely nervous while being so high up. Tim Conway fooling around on the ladder in the scene did not help matters.
When Donovan loses his poker hand to the banker, he mentions "three deuces beats aces over eights". In poker, two pair (aces and eights) is sometimes called the Dead Man's Hand. According to legend, this was the poker hand held by Wild Bill Hickok when he was shot dead.
During the shoot-out in front of the bank, Harry Morgan tells the woman next to him 'cover me, Mildred.' Mildred was also the wife of Harry Morgan's iconic Colonel Sherman Potter on M*A*S*H (1972), filmed at the same time.
The $87k+ gold nugget at $15/oz (based on the gold price given by Don Knotts in the film) would be worth more than $9M in 2019 gold price value.