As a general rule, the best way to resize amigurumi is to change the yarn weight and corresponding hook size. To double the size of an amigurumi, use a yarn
Ophelia the Ostrich Free Crochet Pattern - Hooked by Kati
Ultimate Craft Festival Guide - A Crafty Concept
Chubby Chicken Free Crochet Pattern - Little World of Whimsy
Understanding Round and Oval Shapes (in order to create head
Rainbow crochet pattern that is free, easy, and beginner friendly
Tutorials – Aoibhe Ni
Amigurumi: Make It Smaller or Bigger - Here's How! – Make Me Roar, amigurumi crochet patterns, kit and courses
Resizing Amigurumi – PlanetJune by June Gilbank: Blog
Free Star Wars Crochet Patterns - Sweet Softies