I recall some of the larger plastic pants, designed for older, over 40lb, children had vent holes with a little flap of plastic on the inside. I think the size was listed as "super" and they came in a variety of pastel colors. I recall seeing them as I got a little older. At that time, my mom was buying Klienerts plastic pants which had a covered elastic at the waist and legs which was one of the earliest versions of the non-wicking plastic pants. (Excluding, of course, the Bittner rubber pants.)