They really had to think on their toes

This malaphor comes courtesy of a local Birmingham Alabama news story about firemen rescuing people caught in a flash flood.  A fireman said:  “ The firefighters really had to think on their toes due to the changing conditions. “  This is an excellent example of a congruent conflation, mixing “think on (one’s) feet” and “be on your toes”, both meaning to be alert and react quickly.  Obviously the mix here is “toes” and “feet”.  A big thanks to David Stephens who was on his toes for this one.