Find all 11 Calypso Pieces. There is one Calypso piece on each level to find. Visit this link for locations:http://www.xbox360achievements.org/forum/showthread.php?t=27...
Note: If you are having trouble popping this achievement and it looks like you have all the pieces, look at them like this:
1 2 3 4
5 6 7 8
9 10 11 12
This should help you figure out which level you are missing.
Thanks to Crimzen Dragon
for the guide.