"Dog Day After School" is the twenty-fifth webisode of Season 3.
The webisode starts off with Supergirl racing past the Daily Planet in her hover-pod, just as she gets a Kryptonian proximity alert on her scanner. She sees the damage being caused on her monitor, but doesn't realize she's about to crash into a nearby building, quickly turning to go through the gap in the building. However when she reaches the crime-scene she realizes that the Kryptonian had disappeared.
Back at Super-Hero High, Supergirl is seeing Batgirl in the workshop, who says it was weird that the Kryptonian proximity alert was activated, guessing that the device must be broken, with Supergirl adding that it could actually be working and that some Kryptonian criminal had managed to escape the Phantom Zone. Just then the "Save_the_Day" alarm goes off, with Supergirl realizing it could be the Kryptonian and racing off. In Metropolis, Supergirl is being accompanied by Hawkgirl, who assures Kara that they'd find the Kryptonian if they were out there, just as Beast Boy calls the two over.
Beast Boy reveals that he had managed to find the cause of the Save_the_Day alarm, being something that had torn through the fire hydrants. Hawkgirl then notes that if she hadn't known the culprit to be Kryptonian she would of guessed Para-Demon, just as Perry is caught at a nearby fire hydrant. Hawkgirl then deduces the direction in which the culprit went and the three race off. As they turn the corner, they see a horde of cats running down the street, with Beast Boy attempting to stop them by changing into a cat, but to no avail. Batgirl and Catwoman then arrive on the scene, with Catwoman managing to round up all of the cats, into Batgirl's cruiser.
Supergirl is quick to ask whether Catwoman had seen a Kryptonian anywhere, to which Catwoman says that she hadn't, but notes that whatever it was must of been bad to spook the cats and that she and her fellow cats have a sixth-sense about predators. Supergirl then hears distress calls through her super-hearing and directs the others to the Capes and Cowls café, only to see citizens racing out in fear, as the Kryptonian entity violently ravages the café, before disappearing. Supergirl enters the café, asking Steve whether he'd seen who had done it, but Steve just says that the entity was too fast and wild for him to see.
Hawkgirl and the others then arrive, with Hawkgirl asking which way the culprit went. Steve points the group to the alley at the back of the store, with the heroes preparing for a fight, as they notice the entity, hiding between some boxes. Supergirl creeps forward and bends down, only to notice it as her dog; Krypto, who jumps on her and starts licking her. Beast Boy confused, asks whether the two know each other, as Supergirl explains the circumstances. However Supergirl says that she didn't really care how, but that she was just happy for Krypto to be there as the two hug.
- Anais Fairweather as Supergirl
- Greg Cipes as Beast Boy
- Nika Futterman as Hawkgirl
- Josh Keaton as Steve Trevor
- Cristina Pucelli as Catwoman
- Mae Whitman as Batgirl
- The title is a pun to the film Dog Day Afternoon.