A 1960s Krystal fast food training film included instructions such as:
– Keep your teeth clean and white. Anybody can have a pretty smile.
– Naturally, you don’t want to get too familiar with the customers, just be really pleasant and friendly. Let your personality show through.
– The customers aren’t interested in your private jokes. That kind of horseplay just won’t go.
– Keep your fingers off the food and don’t put the butter on top of the waffle.
[Found here. Unfortunately there’s no link to the video.]