Then what was the professor doing with tall, tin, dark, and creepy?
3 seconds sound clip from Scooby-Doo, Where Are You! - What a Night for a Knight (S1E1).
You can hear this line at 00:04:46.765 in the Blu-ray version of the episode.
Quote context
[...]
- 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?
- He was delivering it to the museum, all the way from England.
- Where do you want it, Mr. Wickles?
- Oh, just put it in the medieval room.
- Right.
- Come on, Scooby, we're leaving.
- Coming.
- This mystery's got me baffled.
[...]