Because Eric killed Ivy, he had to attend her funeral, which he doesn't like, then gets beaten up by Custard as a result.
Eric: I'm bored.
(Diesel and Kate walk in crying)
Eric: Mom and Dad, why are you crying?
Dad: You killed Ivy yesterday so we're going to her funeral!
Eric: No way! I'm not going there!
Mom: Go there or you're grounded!
Dad: Ivy was the nicest daughter of ours. We used to change her diapers and give her a bath. Eric, now it's your turn to share about her.
Eric: Ivy was the worst sister of mine! She always grounds me and David even though I don't mean to kill Barney! She is nothing but a chubby crybaby! I have no sympathy or sorrow for her at all!
Dad: Eric, how dare you talk that way about Ivy! That was the worst and embarassing speech I heard in my life!
Mom: You are lucky everybody in the church didn't come here to scold you! In the meantime, that was even worse than the one you said at your grandmother's funeral! You are grounded for three trillion years! Now, someone will beat you up! Do you know who he is? I'll give you a hint. He is a red and purple Save-Um, and he is also the cool cat-eared pilot of the Zoomer and takes the Save-Ums on the adventures.
Eric: I don't want to be beaten up by Custard.
Dad: Too bad. It's for good. Custard, beat up Eric.
Custard: Prepare for some bleeding.