Ernie the Chicken

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Ernie the Chicken fighting Peter.

Ernie the Chicken has a tenancy to randomly pop up in an episode and have an epic fight with Peter. These fights tend to go on for a long time. In the episode "Da Boom" Peter first met Ernie outside of a convenience store when Ernie was giving out coupons, it turns out that Ernie gave him an expired coupon, this resulted in a long bloody rivalry. And the fight still continues from time to time.

After a few fights, they forgot about why there fighting and Ernie makes it up to Peter by taking him to dinner at a fancy restraunt. When they cannot decide who will pay for the bill, another fight starts.