I also get a chuckle out of Fredo trying to figure out what banana daiquri is in Spanish.

But before Fredo yanks his hand away, he tips off Michael that he's disgruntled, talking about how he was mad at Michael - he doesn't say why at that point, but it's certainly elaborated further in the boat house scene.

Then you see Michael cooly and methodically tell Fredo that there will be an assassination attempt that night, and that Fredo is behind it. You certainly see contrast in the brothers - Michael is calm and collected, whereas Fredo is noticeably nervous in his speech, especially after Michael tells Fredo he's already made his move on Roth.