Why Thog pants turn Purple

[doughboyklg]

Does anyone know what strip number he says this in?

[Precure]

https://www.giantitp.com/comics/oots0387.html

[doughboyklg]

Thank you!

[brian 333]

Dr. Banner, tired of hitch-hiking home naked from wherever Hulk dropped him off in the rain, put his prodigious scientific intellect to work in developing Ban-dex. Ordinary slacks of any color, when stretched beyond the structural integrity of normal fabrics, turn purple and stretchy. The material has, in recent years, been put into the production of yoga pants and adult diapers, the latter of which answers Thog's question.