When to Whistle!

When to Whistle! is a magazine story.

Plot
One day, Thomas is shunting in the yard when Percy comes up behind him and whistles loudly. Thomas is greatly startled and Percy laughs as he puffs away to get coaches for the big engines. Gordon is boasting to Henry when Percy's loud whistling interrupts him. Gordon thinks Percy is very rude for doing so but Percy thinks Gordon is being silly.

Percy continues to loudly whistle throughout the day. This ends up causing water from the water tower to splash onto Duck during his refill and oil to squirt on Donald's face as he and Douglas have their wheels tended to. Percy is later sent out fetch trucks from a main line siding and everyone is relieved to not have to deal with him for a while.

As Percy backs into the siding, one of his valves starts to leak. Duck passes by shortly after and Percy whistles to him for help but Duck thinks it is just Percy being annoying again. The same thing happens when Gordon passes by, who whistles back trying to prove his superiority. Percy begins to grow upset, fearing he'll be stuck on the siding for a long time. Luckily, Percy's driver had telephoned The Fat Controller and Duck returns to bring Percy home. Duck says it serves Percy right and how he should only whistle when it is important. Percy rightfully agrees.

Characters

 * Thomas
 * Gordon
 * Percy
 * Duck
 * Henry
 * Donald and Douglas
 * Sir Topham Hatt

Trivia

 * This story may have served as the inspiration for the eighth series episode Percy's New Whistle.