Can you corroborate this odd hypothesis?

4 seconds sound clip from Batman (1966) - The Joker Goes to School (S1E15) TV Series.

You can hear this line at 00:10:53 in the Blu-ray version of the movie.

Quote context

[...]

- There's a crook behind these handouts.

- What's his angle?

- He may have several. One is to lure you into a receptive pattern of easy living.

- You'll quit your studies, become dropouts. You'll have no other recourse but to join criminal groups.

- Batman's right. It's sort of.... recruiting drive.

- Sure, he's right. What did I tell you?

- Can you corroborate this odd hypothesis?

- What's the crook's name?

- I can do better than that. I can show you his picture.

- What's your name, son?

- Richard Grayson, sir?

- Thank you, Richard. You darken the room, I'll man the projector.

- Roger.

- Here it is, everybody, The Joker. Don't be deceived by that grin, anyone.... He's one of the most malevolent malefactors we've ever met.

[...]