Now... let's see whose glowing phosphorous face Redbeard really is.

4 seconds sound clip from Scooby-Doo, Where Are You! - Go Away Ghost Ship (S1E14).

You can hear this line at 00:19:54.053 in the Blu-ray version of the episode.

Quote context

[...]

- Hey, let's ride! He'll never catch us on this automatic pogo stick... Pogo stick? This is a jackhammer!

- Shaggy! Scooby!

- Look out!

- Look out! The tires!

- We did it, Scooby!

- Scooby Doo!

- Nice going, kids. Uncovering these phony ghosts and their ghost ship is a job well done!

- Thank you, sir.

- Now... let's see whose glowing phosphorous face Redbeard really is.

- Mr. Magnus? And I thought, like, the butler always did it.

- But who are the other two?

- Hired henchmen, I guess.

- Mr. Magnus was just about to lose his steamship line... unless he came up with a lot of money.

- And what easier way than to hijack your own ship and sell the cargo?

- They had a pretty neat ghost setup... even down to the ghost sword operated by wires.

[...]