The alien's first form resembles a tardigrade.
One of the items on Maggie's dresser is a rotund alien suit. This is a nod to the original series episode The Invaders (1961).
The moving boxes in the couple's basement have the name "Dingle", and a logo of a man carrying a vacuum cleaner. This references the original TZ episode Mr. Dingle, the Strong (1961).
Maggie's box of stuff has a clown doll. This is a nod to the original series episode Five Characters in Search of an Exit (1961).
The real estate company selling the couple's home is David Morton Real Estate. This is a nod to the original series episode A World of Difference (1960).