Mister Rogers' Neighborhood (1968)

S3E36 Death of a Goldfish

Rogers discovers that one of the fish in his aquarium has passed away. He honors its memory by burying it and, with Bob Trow's assistance, creates a tombstone featuring a pentagon shape adorned with an illustration of the fish. Meanwhile, in the Neighborhood of Make-Believe, worry ensues when the Trolley halts at the Castle and remains stationary. With the help of Bill Platypus, they soon realize that the Trolley has merely derailed, which is affecting its ability to pick up electricity, a situation Mister Rogers had previously explained.