Hold your breath and don't move a muscle.
5 seconds sound clip from Scooby-Doo, Spooky Space Kook (S1E15).
You can hear this line at 00:07:34.963 in the Blu-ray version of the episode.
Quote context
[...]
- Come on. Let's split up and see if we can find this mysterious ghost from space.
- Well, OK, wise guy, let's see you try that one again. Just try it.
- Hold your breath and don't move a muscle.
- Pilot to copilot, I got an idea. Release the life raft.
- Right.
- Well, it wasn't the easiest escape, but we lost him.
- I hope Shaggy and Scooby are having more luck than we are.
- Shall we look in here? It looks like a shop. Go on in, Freddy. Let's look around.
[...]