Small details in Star Fox 64 that I think are neat
Whenever Arwing gets close to a body of water, trails will appear on the surface.
If one of your wings gets damaged, smoke will appear from Arwing and you will be leaning toward the damaged wing's side. You also will gradually lose height, requiring you to manually keep Arwing in the air. If you damage the other wing as well, you'll stop leaning and start descending even faster.
In cockpit view, you can see Fox's reflection in Arwing's black control panel.
The Dorisbies have a picture of Andross in the front.
Pigma has a different opening line on Fortuna depending on whether you have Peppy with you.
Bill's dialogue at the end of the Katina level changes depending on whether you shot down any Cornerian fighters.
In the Japanese version, instead of saying "Beautiful! I could kiss you for that!", Katt says something along the lines of "Nice~ I'll lick your face later," like a cat she is.
It's really hard to notice, but Slippy's pupils are actually shaped just like a real frog's.