The plastic bag may include flexible thermoplastic sidewalls that have a pattern imparted onto them. The wrinkle pattern may be a plurality of linear ribs formed into the sidewall that may be arranged adjacent and parallel to one another. To impart the pattern to the sidewall, a thermoplastic web used to make the sidewall may be directed between a first cylindrical roller and a second cylindrical roller, each of which may have a plurality of spaced ridges extending about their peripheries. When the web is directed between the first and second rollers, the meshing of the ridges may form ribs into the web.