Johnny is the anthropomorphic steam engine on his mail train and a fictional character among the more memorable characters of the 1950 cartoon, The Brave Engineer, and is one of Casey Jr's friends in Casey Jr. and Friends.
The scene opens where Johnny and the other trains are resting in the railroad, and despite not having a face in the cartoon, Casey's engine wakes up while slow asleep, with his engineer, Casey Jones, waking up in Johnny's cab, and finding that he is late, before getting Johnny ready.
Mail is loaded, and with a toot on the whistle, Casey and Johnny set out of the yard at a high speed, and nearly collide with two trains while climbing a mountain.
Casey is seen relaxing in a rocking chair, putting every bit of coal in piece by piece, and as the train rockets over the mountain, Johnny sinks in the water, before Casey gets up onto the engine's roof, and starts to use his coal shovel as a paddel, and starts to paddle over the water, up and down.
Before long Casey has cleared the track and is on his way again after getting through the rain. No sooner is the train back to full speed, Casey is forced to bring the train to a screeching halt, causing the coal from the tender to land in Johnny's furnace, for standing Casey's way is a brown cow, who gets out of the way, thanks to Casey blowing the whistle, before the train speeds off with Casey shovelling the coal into the furnace.
Later, a villain ties a damsel to the railroad the tracks, leaving Casey to run forward and stand on Johnny's cowcatcher, and scoop up the frightened lady, in the moment in which the train might run over her before the villain curses at Casey, who drops off the damsel at the station.
Hours later, night has fallen, while Casey's engine runs through a narrow, snow covered mountain pass, and through a tunnel toward the trestle. A villain hag, having put explosives on the bridge, lights a fire and flees when Casey's train approaches the trestle. After a mighty explosion, and not being daunted, Casey's engine struggles, huffing and puffing up the side of the gorge, and continues on his way.
As the train speeds through a tunnel, a bunch of train thugs see this and decide that it turns out to be gold on Johnny. As they charge toward the train, Casey is about to get himself and his train attacked by a local gang of train thugs! At first, Casey is caught stoking the furnace with coal, that he is unaware of the train robbers ready to attack him. It is in the next moment that he accidentally picks up one of the train thugs, who is standing on his coal shovel, full of coal, and is nearly shovelled into the engine's furnace. Annoyed by this new distraction, Casey starts to fight the train thugs, while stoking the furnace with coal, and after throwing the train thugs off his train, Casey checks his watch and feels horrified to find that he is late once again.
Determined to make up for lost time, Casey opens the throttle so hard, that he snaps it off its ribbing, causing the train to speed up and rattle, before he throws away the throttle.
The scenery outside quickly becomes a blur as the train travels faster and faster. Casey adds more coal to the furnace, and, when running out, also uses up his coal shovel and rocking chair, until the ribbing on Johnny's boiler exterior is forced off. Casey grabs and fits the funnel back on, before it falls off, when the train speeds down one hill, it heads past a 7 mile sign, and burns it and the tracks. As Johnny's cowcatcher nearly snaps off, Casey pulls it back on, before the boiler gets so hot that the parts fall off, and while Casey manages to fix it time, he bravely gives Johnny some running repairs while the train is seen roaring down a hill.
While otherwise occupied, Casey doesn't notice another train coming toward him on the same track. The other train is a freight train, double-headed by a pair of 4-8-0s, piloting some elder workers. Casey, who is still fixing the dome, has no idea that his train is about to hit the other. As the train speeds round the corner, an elder engineer on the front locomotive while driving, yelps in surprise, and screams in fear, and blows the warning whistle to let the others know that Casey's train is coming. The conductor on Casey's train gasps in the caboose and runs up to tell Casey about the oncoming train, but fails to get the message through, then warns Casey again. As the other train approaches, the conductor blows the whistle, but when Casey refuses to listen, the conductor jumps off the train, and is still seen on Johnny's roof in the next shot. The workers on the other train, gasp in terror, and jump out of their engines' cabs, unharmed, and flee for cover. As Casey finally notices, the two trains collide into each other with a large explosion in a cloud of black smoke.
Afterwards, at a railroad station that Casey is meant to terminate at, with another train on a siding, the porter looks at his watch and sighs sadly, but before he can remove Casey's name, he hears a real life train whistle. Casey arrives at the station in Johnny, who has been broken to pieces.
A beaten-up Casey then shows his watch with pride, which states he is 'ON TIME--ALMOST'. And the Narrator says 'Next time, take the train!'
Johnny is an American Standard 4-4-0 engine, also known as an American type steam locomotive, which was the most common wheel arrangement for steam trains, during the 1800s on American railroads. Johnny is No 2 in The Brave Engineer and is No. 18 in Casey Jr. and Friends, and since Casey pilots Johnny in the cartoon, his real engine in reality on his fateful trip, was a 4-6-0 Ten Wheeler No. 382, because a replica of that is currently on display at the Casey Jones Home & Railroad Museum in Jackson, Tennessee.
Some workers on the other train, piloting two 4-8-0 locomotives, see Casey's train, and gasp, but jump out of the cabins of their engines, and flee in fright for cover.