CI4 - Chicken Multiplicity (Duplicity hehe, they hide inside one another)
CI5 - Chicken Exponentiality
What’s less than multiplying and 4? CI3 Additivity.
This starts with Yolk Star who then summons Sweater Chicken after its first stage instead of yolk, and each piece of clothing removed summons a balloon chicken. Once Sweater Chicken is defeated, it summons the Mother Hen Ship, who can now summon terminator chickens too, which then summons the second stage of the yolk.
Better suggestion provided by @Spamton_g_Spamton
Maybe use sweater chicken → blast from the past and mystery ship → 2 big chickens each → 5 baloon chickens each (they spawn chickens after they fall, too) → 3 chickens each.
Not sure if this should use Yolk Star or regular boss music.