Well, Fredo wasn't the sharpest knife in the drawer. But, since you raised that interesting point, it just occurred to me that, maybe, Fredo was feigning ignorance of how to order a banana daquiri to make Michael think he hadn't been there before under any circumstances--which makes the Superman gaffe all the more impactful for Michael.
Exactly right Turnbull. I've always felt that Fredo was, as you put it, feigning ignorance in that scene.
