Woolly Bear is the 51st episode of Thomas & Friends.
In summer, long hay grows beside the line and gangers cut it and rake it into heaps to dry in the sun. Percy then collects the hay in empty trucks and takes them to the station. There, Toby collects the trucks and takes them into the hills for farmers to feed their animals.
One day, Percy arrives at the station and starts to tease Thomas for thinking he was a ghost. Thomas retorts that Percy is a "green caterpillar with red stripes", which makes Percy angry. Thomas then reminds Percy that he has been late at the station every afternoon that week. Percy tells Thomas that it is the hay that is making him late, but Thomas is not interested in Percy's excuses and Percy leaves.
Percy grumbles to himself all that afternoon that he is only ever late by a few minutes, but nevertheless he and his driver decide to head to the station earl after going to the harbour to drop off some trucks. At the harbour however, there is trouble; a loose crate of treacle hanging over Percy drops and splatters all over him. The workmen at the harbour try to clean him up, but Percy has to leave and is still very sticky when he does.
Soon Percy comes to the hill where the hay is laying and by now it is very windy. The hay is blown over the track and Percy. Because Percy's wheels slip on the slippery hay he must wait for the line to be cleared. While he does so, the wind blows some of the hay onto Percy, where it clings to his sticky boiler.
At the station, Thomas waits angrily for a late Percy. Suddenly, all the passengers start laughing when Percy arrives as he is now completely covered with hay, making him quite a sight. Thomas laughs that the "caterpillar has crawled out of the hay". Percy does not know what Thomas is talking about, but Thomas tells him that seeing Percy like this is worth being late.
Percy runs back to the shed where his driver shows him what he looks like in a mirror. Now Percy knows what everyone was laughing at, stating that he looks like a woolly bear and asks to be cleaned before Toby arrives, not knowing that Thomas has already told Toby everything.
In the end, it does not matter as by the time Toby and Thomas arrive, Percy is still a long way from being cleaned causing the two to make jokes about woolly bear caterpillars. Percy does not find these jokes very funny at all.