In episode 644 the crew left on the boat get transformed into some "Artistic things".
What exactly are they symbolising? For brook it was pretty obvious, as it was the screamer. But I couldn't quiet put my finger on the other ones.
They're all a bit based on the arts of Okamoto Taro mixed with some unique traits; like Brook based on the screamer, Nami on some Taro statue, Momonosuke (Samurai Dude xD) based on fantasy, since Momo in Japanese means peach xD, and for Chopper I can't remember xD.
The Sunny also is probably based on Taro arts, as the figurehead is a representation of the Sun Tower of Osaka as you can see here: