It doesn't matter what it's like. It's a Bog of Eternal Stench.
6 seconds sound clip from the Labyrinth (1986) movie soundboard.
You can hear this line at 00:55:31 in the Blu-ray version of the movie.
Quote context
[...]
- I've never smelled anything like it. It's like...
(BOG MAKES FARTING NOISES) (2)
- It doesn't matter what it's like. It's a Bog of Eternal Stench.
- Help!
- What did you have to go and do a thing like that for?
- Do what? You mean rescue you?
[...]