One of the altar boys serving was the star of our high school basketball team (in a town of 300). He was gangly and well over 6' tall. When he went to stand up after kneeling at the side of the altar, the back of his cassock caught on the heel of his shoe and he stumbled backwards across the sactuary with his arms flailing until he landed on the bench against the wall where Father and the servers sat.
When I looked up to see what our very ancient and stern priest was going to do, he was just standing there behind the altar looking straight ahead with his arms still raised, tears in his eyes, and his face screwed down as tight as he could get it to maintain his composure. And he stayed like that for a minute or two until he could continue.
You'd have to have been there to appreciate it, but that is still one of the funniest moments I can ever remember from Mass. It still makes me laugh when I think about it.
That’s what happens when your cassock is too long. You kneel, and it drapes over your heels. You stand, and step on the thing ... then you’re in trouble. For a growing boy, consistently having a properly sized cassock can be a challenge.