6. Katee Sackhoff

Source: Twitter @RoadGraphs/ CBS
Katee has some of my favorite recurring cameos on Big Bang. As Howard’s fantasy girl, the Battlestar Galactica actress has appeared a couple of times to give him advice, usually in his love life.
7. Neil deGrasse Tyson

Source: Twitter @euge_quin
One of the best things about cameos on this show is that they blend reality with fiction. On deGrasse Tyson’s appearance in season 4, Sheldon scolds him for the hand he played in Pluto’s infamous demotion from planet to dwarf planet. We’re still angry, too, Sheldon.
8. Bill Nye

Source: Twitter @Dc17C15/ CBS
Oh Bill Nye, how I love thee. When “The Science Guy” appears in season 7, his storyline is related to Bob Newhart’s. Nye ends up befriended Sheldon, the lucky devil.