Penguins!

While the penguins are engaged in a training exercise, Eggy the duckling enters the HQ, acting in a commando-like fashion. His mother soon locates him there, and tells the penguins that Eggy has been behaving that way ever since their egg-watching adventure. As requested by Eggy's mother, the penguins agree to work with Eggy to convince him that he is not suited to engage in their para-military operations. But when he persists in desiring to become a commando, Skipper leads Eggy to believe that he needs to have a "Penguin Commando License" in order to partake in their operations, and that being able to tackle all the zoo has to offer is requisite for obtaining such. Although briefly successful, this plan soon backfires when Eggy begins to take down all the zoo animals, using the specialized characteristics of each of the penguins that he had learned from them while still in the egg state. Eventually, Julien is the last animal that Eggy had not yet beaten, and thus the only thing standing between him and his "license." But Julien, upon learning that "[his] J.J." (Eggy) wanted to become a penguin, begins dancing to music, and Eggy fails to bring him down as a result. Eggy is then cured of his commando desires but, to the dismay of the penguins, now has taken up Julien's behaviors.