What I always thought was a screw up was when Michael asks Fredo to show his visitors a good time in Havana you presume Fredo knew lots about Havana.

He even talked about how Johnny Ola brought him to some joints that old man Roth would never go to. When he first gets to Michaels hotel with the money he tells Michael what a great town Havana.

But the screw up to me is when Michael and Fredo go for drinks and Fredo asks Michael how to order (what to say) a banana daquiri. Why wouldn't Fredo know that? Better than Michael by far you would think!