Wilhelm Scream?

K, I've seen a few eps because my 5-year-old son watches it (over and over lol), and I'm an old man at 37 :D

He recently noticed a particular scream... in stuff he's been watching: Star Wars, Indiana Jones, etc. etc. so I had to go and explain to him about the Wilhelm Scream and now he points it out every time there is one...

Anyway we got home the other day, flicked CN on and the show was on, already started. And up popped a Wilhelm Scream, so we had a bit of a laugh about it.

Can someone tell me which ep it was in? There were some police types or ninjas or something on the screen at the time but sorry, I'm not Ben 10 enough to explain further. I'm more of a Clone Wars fan :/