
...which would be evidence
of a PLANET orbiting it.
The Big Bang Theory Season 4, Episode 9

...when the PLANET Krypton exploded.
The Big Bang Theory Season 2, Episode 11

Unlikely, but it could be a dwarf PLANET.
The Big Bang Theory Season 9, Episode 12

living on a PLANET populated
with nothing but chimps.
The Big Bang Theory Season 5, Episode 21