Where did I get a dog?
I have a dog now. He's sitting in The Odyssey with his little hat on. Doesn't do much.
I'm pretty sure I didn't buy one of those, and there's no dog in my souvenir list. Where the heck did I get that? What's the trigger?
Solution 1:
From the Super Mario Wiki: "the Dog appears inside the Odyssey after finishing the game at least once..."