This was way over my head [the meaning] but I have a good visual of Charlie spitting soup!lol!
It is just about how people share silly moments and from those moments come sayings or quotes that have meaning to them and few others. If you take a bite of cracker, then spoon in some soup...no problem...if you go with soup first, it may run out when you try to put in the crackers. So her advice to a dribbling Charles was to go with the crackers first. And that became one of those inside jokes among us.
"FIRST YOUR PANTS, THEN YOUR SHOES."
Excellent advice. Shouldn't there have also been a sign about keeping the hair on both sides of your head about the same length?