Oh, dear, oh, dear. I suppose I should thank you for finding the Black Knight, but with Professor Hyde White's mysterious disappearance and all, I wish you hadn't.
11 seconds sound clip from Scooby-Doo, Where Are You! - What a Night for a Knight (S1E1).
You can hear this line at 00:04:20.769 in the Blu-ray version of the episode.
Quote context
[...]
- Hey, what's this? It's a delivery label that says, Deliver to the County Museum.
- So that's where the old knight was headed for.
- That's using the old noodle.
- But, like, what happened to our mysterious professor?
- Well, if he was driving this truck, he's disappeared.
- Well, gang, it looks like we're up to our armor-plates in another mystery.
- Legend?
- Yes. The Black Knight is supposed to come alive when the moon is full.
- Like, wow! The moon was full last night.
- Then what was the professor doing with tall, tin, dark, and creepy?
[...]