When you study Freud in school, you might think that the idea of oral fixation is rubbish. Until one day you are sitting in a bar during happy hour and you notice the number of women who are doing the following, at the same time:

holding a glass-drinking
chewing gum
putting a red plastic straw in their mouth (swirling it around)
talking non-stop
sitting next to a plate of snacks-eating

Then you start thinking, maybe Sigmund was on to something.