How do you know if a Furby is a rare one?

To know if it is rare, the aproximate date is needed. Any toy that i probably worth any money at all would be from 1980's and before then. If you are talking about "special" prizes, then they come out of the egg in a different colored "yolk" case. For example, the "special" prizes of Smurfs and Sheep come in an orange yolk, while all of the other toys come in a yellow yolk. If you have any doubts, look online for collectors and the year/set it came in. If you are still collecting them, remember to always keep the piece of paper that talk about your toy and shows the picture. This adds a litte more value to them. Italian and German eggs are the most popular.