David Hyde Pierce was offered the chance to reprise his role as the voice of Abe Sapien. But Pierce felt that Doug Jones' voice should have been used in Hellboy (2004) and he turned it down so that Jones would get the role.
The psychic foresees an umbrella. While it doesn't seem like much at first, we later see a tsukumogami take the form of an umbrella.
The name that the old man is carving into a cucumber is "Murakami". Director Tad Stones says that this is a shout out to his friend, fellow animator Glen Murakami
In the scene were Hellboy is talking to the Daimyo's daughter, the statue in the background is making a 'rock on' hand sign.