Well, it's obvious, isn't it? The sailor in the back is wearing a shirt made of nylon when everyone knows they really only wear cotton (or other natural fibers) when dressing.

Make that two errors. From the placement of the subjects it's almost impossible to see that the parrot is holding a knife and is about to take out the captain before he can reach the pistol (the signal being when the "Macarena" stops playing).

Orrrrr, I could be completely clueless. Let's go with the clueless option, shall we?