noun, plural ding·us·es. Informal. a gadget, device, or object whose name is unknown or forgotten.

Is there an animal called a Dingus?

Ok first, let's define the term dingus just to make sure we're all on the same page. A dingus is a dog that, hard as they try, just can't be smooth.

Who says Dingus?

I re-watched Stranger Things 3 and tallied all the times Robin said the term “dingus” in the new season. By my unofficial count, Robin says it four times over the course of the season, including her first line of the series. And, you can see that below, via Stranger Things Twitter account.