Though the pattern calls for two colours and stripes, I just used Caron Chunky Cakes Yarn (Sweet and Sour), which stripes naturally. It's a 6 ply yarn so is thicker than the 4 ply that is recommended. I used the same size needles as in the pattern (5mm) so it's thick and sturdy.
I made a medium one. My sister had given me Frankie's measurements and it came out exactly as the pattern said it would. I hope it fits him.