When the Stooges arrive at the blacksmith's shop, the road dust that were on their clothes disappear when they go inside.
Curly's glasses appear and reappear between shots after he shoots the cracker.
As Blackie grabs the ring back from the Minister, you can hear off-screen laughter.
The hammer that Moe uses to free Curly from the collar bounces a few times when he sets it down, revealing it to be a rubber prop.
When Curly shoots the balloon, you can tell he did not really fire his gun.
The sliding wire on the lit dynamite stick can be seen when it launches into the shack where Blackie and his henchmen hide in.