The planet in question is in fact Magrathea.
3 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 3 sitcom.
You can hear this line at 00:05:42.888 in the Blu-ray version of the TV Series.
Quote context
[...]
- Why not?
- Hey!
- I think It's just any old dead planet.
- Stress and nervous tension are now serious social problems in all parts of the Galaxy.
- The planet in question is in fact Magrathea.
- And the untimely creation and sudden demise of a bowl of petunias, and an innocent sperm whale.
- This fact may safely be made the subject of suspense, since it is of no significance whatsoever.
[...]