An easy way to get Mystery Goos is to go out on the deck of the ship in Neverland. If there are no Yellow Truffles there go back in the ship, run around for a little, and come back out. When there are Yellow Truffles, fly up to one and hit it. Now when it's about to land on you hit it again. You can keep doing this for 100 attacks. There is a high chance it will drop a Mystery Goo when you hit it 15 (or 10 I'm not sure), 50, and 100 times into the air without letting it fall. Also you get tech points, for example: 1st hit: 1, 2nd hit: 2, 3rd hit: 3, ..., 98th hit: 98, 99th hit: 99, 100th hit: 100. And if you hit it 100 times you will get a total of 5,050 XP.