Brenda's Secret is the 5th webisode of Super Hero High. It is similar to The Cat Who Cried Wolf. It also introduces Erin Nygma and Gxyzptlk.
Brenda Wayne has kept her family secret under lock and key. But when Erin Nygma and Gxyzptlk threaten to unravel her secret like a ball of yarn, can she and Alexis figure out a way to stop them?
Brenda is seen running and leaping across the roof tops with her pet cat, Bastet and other cats. She tells Bastet and the other cats that she would love to race again, but she has to get back to school. But one of the cats accidentally flips up her hood revealing cat ears and a pair of goggles. Embarrassed, Brenda tells them all to go find her mother and they all leave. What Brenda doesn't know was that Erin Nygma and Gxyzptlk were watching the whole thing and they both giggle mischievously. Later on, while walking through the park, Brenda hears a familiar voice that says "You can actually talk to cats. How do you do it? We're all ears!" She turns around to see Erin and Gxy sitting on a tree branch with their pets. Brenda tells them not to tell anyone but they both just giggle and disappear. Alexis later on shows up and Brenda hisses at her, but stops when she realizes it's just her. Alexis figures out that Brenda is hiding something. Brenda decides it's time to tell someone the truth. She reveals that she is not only the daughter of Batman, but Catwoman as well, which goes against Super Hero High's traditions, and none of the other heroes and villains know about this. Alexis assures Brenda that she will keep her secret, but isn't worried about her as she gazes at Erin's question mark poster. Later on at Gym Class, Mr. Grant is having Brenda, Felicia Minerva and Arthur Curry Jr. run laps, when Erin and Gxy appear and signal Erin's puppy Puzzle and two of Erin's lackeys who are carrying a small cage and when Puzzle opens it a yellow canary flies out which causes Brenda's instincts to kick in. Alexis is suddenly worried about Brenda. As soon as the canary flies away, Brenda stops running and starts feeling embarrased. Erin then says, "So Brenda, anything you want to, uh, tell us?" in a mischievous voice. Alexis then comes up with an idea to help Brenda. "I can't believe the speed ray I shot your shoes with actually worked! Erin, confused says "What?" "I'll show you." says Brenda shooting her shoes with a ray gun that causes her to run off uncontrollably. Gxy, still around, just says, "You can't get rid of me that easily, Lexi." Alexis just shrugs and says, "Oh, well. Go ahead and tell them Kltpzyxg." Gxy angrily yells, "Not Kltpzyxg! Gxyzptlk! Now as Erin was sayin-- Oh, nuts!" Gxy, just like her father disappears back the the 5th dimension. Brenda walks up to Alexis and says thanks. Erin, still under the affects of the speed ray, runs by screaming. Alexis says, "Don't worry, Erin. It'll wear off... eventually."