Most Creepiest Christmas Scene

So I was watching, "National Lampoon's Christmas Vacation" last night. There was this one scene that I never really focused on until last night. You know the one. You don't? Let me refresh your memory.

So Rusty brings Clark a cat that's been wrapped up on accident by Clark's aunt. Then Cousin Eddie brings over a leaking present that turns out to be lime Jello. That's not really the weird part. Then Ellen tells Eddie to go in the other room. Eddie then looks at Russ and goes, "Come here boy", then pretends to punch Rusty a few times while shouting, "Woo Woo Woo"! Here's the creepy part. He then says to Rusty, "Let's go find your sister".