Day of Fun-Ship is the eleventh webisode of the third season.
The webisode starts off in the air, as Starfire flies a kite while Blackfire hangs onto the string to it. As Blackfire struggles to hold onto the end of the kite, Starfire expresses how glad she is that her sister was there for their sister togetherness, asking whether Blackfire loved their day of fun-ship. In response Blackfire sarcastically says "yay".
In the park, Starfire and Blackfire buy ice cream, with Blackfire taking her first lick of hers and then getting a brain-freeze. Starfire then tells her that she won as her brain had frozen before hers, explaining that on earth, they celebrated the win, by dumping drinks on the winner's head. Starfire then picks up the barrel of cold drinks, asking the vendor to put it on her tab. Still suffering her brain-freeze, Blackfire then gets all the drinks dumped on her. As Blackfire, drenched pops out of the cold pile, Starfire announces she has the most fun way to celebrate their day of friendship.
Blackfire, in response suggests sitting down quietly in peaceful reflection, with Starfire then calling her the silliest sister, revealing that she had meant a trip to the zoo, carrying her sister off. At the zoo, Starfire presses her face against a fish tank, making fish-like faces to a nearby fish in the tank, as she asks her sister whether she believed it to be the most fun, but Blackfire then says that she believed they had different ideas of fun. In response Starfire asks her whether she'd like to and visit any of the other animals, noting giraffes and polar bears, but Blackfire tells her that she's had enough of the earth animals, asking what King Shark's meant to be, as he throws barrels at the citizens.
As Blackfire calls King Shark ridiculous, Starfire notifies her that King Shark isn't a zoo exhibit, but is instead King Shark. King Shark punches a hole in the fish tank, remarking that he was hungry for a fish fry. Starfire exclaims that they must stop King Shark, before flying off to so, with Blackfire close behind. Starfire then blasts King Shark with one of her starbolts, exclaiming that the fish were not for eating, with Blackfire then joining in and firing at him as well.
King Shark then says that no little girls would get in between him and his dinner, grabbing Blackfire by the arm, telling her that she could be his dinner instead. In response, Starfire quickly uppercuts King Shark, freeing her sister. Starfire then floats in front of cardboard cut-out of a mermaid, causing King Shark to ram at her and get stuck through the mermaid cut-out. King Shark then breaks free, as Blackfire asks her sister what they should do. Starfire then grabs the reef decoration from the zoo wall, reminding her sister of the nursery rhyme they had heard when they little. The two girls then quickly circle King Shark with the reef, while singing the nursery rhyme, finally managing to tie him up. The two sisters then finish up by high-fiving in celebration of their day of fun-ship.
At the Boom tubes, Starfire is saying farewell to her sister, as she heads back to Korugar. Blackfire says that's she's now heading back to Korugar, asking whether she'd see her sister back on Tameran for Sovereign day, with Starfire assuring her that she wouldn't miss it. Blackfire then thanks Starfire for the day, saying she had fun, with Starfire then giving her a hug in response.