Mister Rogers' Neighborhood (1968)

Season 13: Episode 7

Mister Rogers arrives with two pieces of wood which were given to him by Bob Trow. Using his imagination, Mister Rogers thinks of many things that the pieces could be used for before he sings You're Growing. Mr. Trow stops by with what appears to be a regular chair but Mister Rogers quickly realizes that when combined with the two pieces of wood, it becomes a rocking chair.