That Cessna 150 on a hot day.

She won't fly if it's a big guy.

My friend, a flight instructor, told hilarious stories of training some larger students in a small Cessna 150 in which the door barely closed and on hot days, the weight was too much for the airplane to do much more than barely get off the ground. The airport they were training from had hills around it and they couldn’t really do a lesson on those days.