This is the first time that other members of Thing's species are shown.
It is confirmed that Thing is a male of his species.
Ted Cassidy played Thing in most episodes.
The little boxes, which contain the Thing creatures, are picked up easily by other characters, meaning that Thing's entire being is inside. He's not just a person hiding under the table and sticking his hand through the box. However, the boxes are smaller than the creatures themselves, and are capable of containing other objects simultaneously.
Vic Mizzy's theme for Thing is heard for the first time. It first plays in musical box form when Lady Fingers is introduced, and then a fuller version is heard when Fingers meets Thing.