Such cryptic hints, I love it! I'm looking for it now.

One last question though, do I need the Squirrel suit at all? 

I agree, secret is secret, I remember the first time I found a secret level in smw, it was awesome, its a great feeling and memory.

I'm pretty sure you don't, for either of them. Castles tend to give Ice Flowers, after all.

I scared Nabbit out of Urchin Shoals, but now he's just gone. What's the metric for him appearing? One P-Acorn plus the ability to quit stages, and i'll have that third star coin and break through to the other side.

I think Nabbit appears after you complete a certain number of levels. I could be wrong.

great fun lol some of those star coins are ridiculous!!!

All star coins collected. "Follow that Shell!" is tricky, although you can break the stage with the penguin and P-Acorn suits, i did the star coins there legit. Third star coin of Pendulum Castle was hard until i remembered that if i could afford to take a hit, i could break the otherwise sinister challenge of the final pendulum rather easily, though it's still hard to get out to that ledge.

Ugh, that third coin was probably the most frustrating for me in the entire game. I couldn't even benefit from using the power acorn because I would always get hit before I got to it. I died probably close to ten times in a row trying to get out to the ledge before the floor disappeared.

All star coins collected and

Me and my brother