We had the milkshakes at Peter's Drive-in for dessert and it was awesome. One price fits all is a great business model and you can mix flavours so selection is excellent. They have other food too and definitely a must whenever you're in a Calgary. Long line up even late at night.
Here's my Vlog on Peter's Drive-In features at 0:13
https://youtu.be/c7BIYunlnHQ