Garp's actually a good grandpa.

There are different types of pirates: The Morganeers, the typical pirate; and the Peace-mains, the ones who destroy those, the good pirates.

Luffy's body is ridiculously more goofy, resistant, and creative.

Luffy's personality is more rational, more contained, and was reluctant to help Anne at first. He has the same fit but his hair is shorter as a kid. She is a little more demure, and her backstory is actually wholesome. Her pet bird is named "Balloon," and super rare bird. The villain was all-rainbow and 100% crew-sacrificing and evil.