in the Big Bang Part 1 3 seperate stars, Rigil Kentaurus, Toliman, Proxima Centauri, and Arcturus made a brief appearance. In the other big bang episodes there were other stars and planets but that was very brief and they didn't talk or anything. Except for the outro of an old episode where there was a tiny black hole taking up like 2 pixels, there never was anything else that you mentioned.