So, I'm poking around the Animal Crossing disc & there are a ton of .bin files. I tried opening them using Stuffit Expander on my Mac. Is there any way to see what the files contain?
Most likely, they are compiled binary files, much like a .dll file on a PC. Try opening them with a hex editior like winhex. EDIT: I just noticed you said you have a mac. Winhex won't work on a mac, i'm not sure what's out there for you, just look for a hex editor.
Chances are unless you have the GameCube SDK, you won't have whatever tool that "might" be able to open it. Whatever the files are, I truely doubt they are all that interesting to look at unless you have some expertise and some kind of goal.