The Liquidator guesses it must be something else.
4 seconds sound clip from Darkwing Duck - Life, the Negaverse and Everything (S1E35).
You can hear this line at 00:01:35.259 in the DVD version of the TV Series.
Quote context
[...]
- Another day, another major crime. Well, see ya.
- Oh, come on, Negaduck, you never hang out with us after a caper.
- Gee, Quackerjack, why do you think that is?
- No, that couldn't possibly be it.
- The Liquidator guesses it must be something else.
- It's because you've got a secret hideout.
- There you go, Megavolt, that's using the old dry cells.
- We don't have a secret hideout. Why can't we go to your secret hideout?
- If I let you go to my secret hideout, it wouldn't be a secret hideout anymore!
[...]