His pants fell to his ankles, so he took them off too.
Wait until you are eight or nine months along, and he kicks you so hard your pants fall down.
The big man's belt buckle tore loose and his pants fell down.
When he spread his arms, his pants fell way down.
Even so, he wears overalls because "otherwise his pants would fall down."
His pants fell open and peeled away with ease to drop to the floor.
Superman then asked the visitor if his pants would fall down without the belt.
"I don't believe they are," Roland said, and let his pants fall.
At the end of the dance the pants snap and fall off.
If he takes a hit with no jacket, his pants fall off, leaving him to run around in his underwear.