This is a fantastic case that really gets to the heart of why English can be so maddening and delightful.

I fall firmly into the camp that insists on "my friends and me" as the object. The "remove the other party" test is the most elegant and unassailable rule of thumb we have. If you wouldn't say "The surprise party was a complete surprise to I," then you certainly shouldn't say "to my friends and I." Grammar rules exist for clarity, and this one provides a clear, simple check.

Saying "a whole other thing" is perfectly grammatical, but it lacks the same emphatic, rhythmic punch. The infixation in "a whole nother thing" creates a clear, almost musical emphasis on the new, separate category being introduced. It's an idiom that has earned its place through utility and expressiveness, not grammar rules.

So, while we shouldn't teach it in a formal grammar class as "correct," it's equally unhelpful to dismiss it outright as "wrong." It's a colloquialism—perfectly at home in informal speech, storytelling, and advertising because it's immediately understood and highly effective. It’s a great example of the language evolving to fill a communicative niche that the standard form doesn't quite satisfy.