Regarding the Canadian vs. US $20 bills, two different productions were made of Degrassi: one to air in Canada and one to air in the USA. Cultural references were adjusted slightly, that's all. I've seen both versions of this episode. The one I borrowed from the Toronto Public Library (Canadian) shows a 1970/1978 issue Canadian $20 bill, whereas the one I got from WGBH shows the classic US $20 greenback.