Casey Krinsey is an average, frumpy teenage girl with pale skin, green eyes, and short light brown hair. She wears a purple short sleeve buttoned shirt, gray skirt, white socks, and brown shoes.
In her Mega form, she combined all the Super Hero Girls' powers, so she looked like a mix of all the girls in their superhero costume.
In her encounter with Zee and her friends later on, Casey is shown to be very nice, and willingness to help out whenever she can. She also is shown be an organized planner, clearing time on Zee's calendar. In truth, however, she is a stalker, who was obsessed with Zee, wanting to obsessively be her friend, and actually be Zee due to her being popular and beautiful. This stems from her lack of self-confidence, believing nobody likes her. When rejected or confronted with her shortcomings, she is shown to be somewhat insane. When her negative traits clash, Casey becomes incredibly angry and violent, willing stop at nothing and destroy anything in to obtain beauty, popularity, and power.
- Power Absorption: Casey possess the ability to steal the powers of others. Shes does this by turning her body into a crystallized form so that the other person shows in the reflection of her body. She not only takes the powers of the person in question, but their physical appearance and voice as well. Given how she was able to replicate all of the powers and abilities of the Super Hero Girls Casey can be regarded as a powerful user of this ability with seemingly no limit of the powers she can have, with her obsessive self-loathing personality making her all the more dangerous.
- In mainstream DC Comics, Casey Krinsky is a somewhat obscure character first appearing in Firestorm vol 3 #4 as an adversary of the second Firestorm, Jason Rusch. To which she developed a psychotic infatuation.
- As of the episode "All About Zee," Casey knows the secret identities of all of the Super Hero Girls. However, due to her unpopularity and Zee's fervent instance of who she was when transformed into Casey, when Casey attempted to convince others, they ignored and mocked her, most likely thinking her deranged.
- It's unknown if Casey will return as she vowed Zee that she'll get revenge on her and her friends.
- She’s the only main antagonist that became corrupted.