Carly "Cee" Catto is a student at Keaton School of the Arts, studying in the Dance Program. She is the ex-girlfriend of Sasha and Austin and best friend of Vanessa Morita. Carly is portrayed by Alyssa Trask.
Vanessa was chosen as Prima out of the freshmen, and made plans to go an ice cream shop with Carly after school ended that day. However, some of the upperclassmen invited Vanessa to go with them to watch a rehearsal at the National Ballet. Vanessa went, after talking to Carly. Carly was "happy for her" but was disappointed at not being Prima, though she expected it.
In "Groups of Two" Carly and Vanessa danced to a routine they had made up years before, impressing Sasha and . Vanessa was making an attempt to not make a big deal out of being a Prima, but it just made Carly uncomfortable. They talked in a group, Jenna asking Vanessa plenty of questions. Later, they were put in pairs to choreograph a dance over their own, and Carly was paired with Sasha. Vanessa was paired with Jenna, and Vanessa started to teach her the routine that Carly and she had done, upsetting Carly. When the two of them began arguing, Sasha listened, wanting to blog about the gossip. However, seeing them upset, he talked with Vanessa, giving her advice. Carly performed her dance with Sasha and Helsweel commented that she "didn't hate it." When Vanessa tried to talk to Carly, Carly walked past her and started dancing to a song called, "I Don't Wanna Hear It (No More)".
In "Take Me Out" Carly and Sasha were practicing their duet in front of the class. After that, Vanessa and Carly are stretching when Vanessa asked why Carly didn't tell her about Sasha. When Carly asked back, "What do you mean?" Vanessa tells Carly that Sasha is smitten, but Carly continues to deny that Sasha likes her. After class, Vanessa approaches Carly with their stress basket. When Carly asks why Vanessa is giving this her this, Vanessa says to "Eat some blueberries, it will relive the anxiety". The two continue to go on like this "Are we really playing this game?" When Vanessa says "So aren't you worried about your dance chemistry?" Carly responds "Am I hiccuping? No, no hiccups. No worries, so your wrong." Carly then says "Ever since I was a kid, my body manifests how I'm felling by hiccuping when I'm worried, sneezing when I'm scared and tugging on my ear when I'm angry." The two continue to bicker about this for the next few seconds. Then Vanessa says "Fine, I will face it, right after Sasha passes my test." Vanessa had taken Carly's phone and sent Sasha a text saying "Coffee 911! Pleeease?" After Sasha got her complicated order corrected Carly responds by hiccuping. When the two are rehearsing later that day, Sasha drops Carly. When Carly's in her talking head right after, all she does is hiccup. Carly tries to talk to Vanessa about what to do but all Vanessa says is to talk to him, but Carly isn't sure how to go about that. When Vanessa askes her if she likes him back, she has a definite answer of no. So Carly for the rest of the afternoon, Carly hides from Sasha. Though by the end of episode, Carly seems to have a change of heart, says that she likes and trusts Sasha.
In "Dig Deeper", it's Cee and Vee's 9th friendaversary. Since Carly is a bit worried whether Sasha likes her back or not, Vanessa cheers her up by taking her to eat ice cream and watch a movie the next evening. Carly agrees until Sasha comes and invites Carly to go with him to Shawn Mendes' concert that very next day. He had two backstage passes to meet him and he apologizes to Vee for not inviting her. Carly agrees to go with Sasha. Vanessa reminds Carly about their plans but Carly says that they could do that another time. Vanessa leave, angry. Both Carly and Sasha were confused as to why she was so upset, but then Carly remembered that it was their friendaversary and called herself the worst friend ever. The following day, she brings Cee an ice cream sundae and balloons and apologizes to Vee about blowing her off.