Blue Engine Blues - S2.E37

A rough night's sleep and a cancelled beach day puts Thomas in the grumpiest of moods. Encountering Riff and Jiff with their usual happy-go-lucky attitudes, Thomas comes to the conclusion that he'll only be liked when he appears happy. He puts on a fake smile for the rest of the day, but his words don't match his demeanor and everyone can see right through him. Finally, Thomas comes across Riff and Jiff again, who reveal they're also upset about the cruddy day!