Claude's two dominant traits are his Sharp intellectual Mind and his utter fearlessness. Even thou he is very mature Claude can still easily be amazed by the simplest things, such as hermit crabs. He likes monsters and will ask weird creatures to join his crew (as seen in the Thriller Bark arc, asking a talking tree to join his crew). He is calm, collected, and highly perceptive. He also seems well aware of the terror his reputation inspired in his foes. He appeared to be respectful of those around him; and doesn't like to freely speaking about others' pasts.