Never fly with a full bladder
Wasn't sure what forum I should put it in but it was from an ex-military pilot who probably saw stuff like this during service before becoming a test pilot.
About Mutt Summers.....
Jock Bryce recounts that on his first flight with Mutt in the prototype Viscount 630 he was astonished to see Mutt beginning his pre-flight checks by relieving himself alongside the main wheels. “Never fly with a full bladder,” was his advice, “I know people who crashed with one and it killed them!”