[mike777]

© A fielder, after catching a fly ball, falls into a bench or stand, or falls across
ropes into a crowd when spectators are on the field;
Rule 7.04 © Comment: If a fielder, after having made a legal catch, should fall into a stand or
among spectators or into the dugout or any other out-of-play area while in possession of the ball
after making a legal catch, or fall while in the dugout after making a legal catch, the ball is dead
and each runner shall advance one base, without liability to be put out, from his last legally
touched base at the time the fielder fell into, or in, such out-of-play area.

Never heard of this rule or seen it enforced. I wonder if the players know about it?