Capture 20 Gumducks
Gumducks are a type of “animal” you are required to capture during the “Gumquack Hollow” main quest before facing the Porky Puff world eater. You are tasked with going into a location called “Gumquack Hollow” to capture these for Goop. It's location is one the border between Bricktown and Surfipelago.
At the end of this tunnel location, there is a large room with shallow water in it, where you find a number of rubber ducks floating around, which are the Gumquacks you need to capture.
This one specific area always respawns several Gumquacks, so to get 20 you can simply farm them by returning to this location a few times.