The pet whose death Mister Rogers addressed in the March 23, 1970 episode was a goldfish.
The episode, commonly identified as “Death of a Goldfish,” begins when Rogers notices that one of the fish in his aquarium has died. He buries the fish and makes a small tombstone, using the moment to speak plainly and gently about sadness, memories, and saying goodbye.
The subject is sometimes confused with the childhood dog Rogers also mentions in the episode. He recalls how he felt when that dog died, but the animal that has died in the televised story is the aquarium fish—a goldfish in the episode’s title and descriptions.
This was part of the show’s distinctive approach to difficult subjects. Rather than avoiding death, Rogers acknowledged children’s grief and explained that feeling sad is natural and that memories can remain meaningful. The episode aired during the show’s third season and became one of its best-known discussions of loss.