I made the blue superhero bag first, using a regular plastic bag as the template. It's not as big, the stitches aren't as pretty but I did include the fold-in pocket so it carries around really easy. Since this was to be the boyfriend's bag, it's didn't have to be pretty, just functional. With the pink bags I regrouped and made some changes, making a sturdy template from a cereal box using the roomier target plastic bag. After cutting out everything, I assembly-lined the shopping bags. These don't have the pocket, since I used the extra fabric to make another bag instead.
I've taken them out to the grocery store twice now, and they can hold quite a lot. Even with the heavy loads, they hold up well and don't cut into my fingers! Even the boyfriend is a fan!