Mysterious Part ID help, clear blue disk with electronics inside My kiddo has recently been given a random parts grab bag, and we’re unable to ID one particular item, of which he has three: anyone know this part?
That's a LEGO Dimensions Toy Tag, used  to connect the physical toys to the now discontinued LEGO Dimensions game. See it here: https://www.bricklink.com/v2/catalog/catalogitem.page?P=18603c00a#T=C&amp;C=15

Yours is the plain kind (no printing on top), which means it was not used for a minifig, but for one of the small builds in a LEGO Dimensions set. Here is a list of all the sets the part you have appeared in: https://www.bricklink.com/catalogItemIn.asp?P=18603c00a&amp;in=S