Cassie Scerbo's energy is so warm and enthusiastic that it's hard to believe she would play the mean girl. (The actress even put a positive spin on being stricken with a crippling case of food poisoning!) However, portraying the frenemy is the exact challenge that Cassie is excited to embrace.

Cassie will stir things up on 'Baby Daddy' in a two-episode arc, the first airing on Feb. 26. She chatted with PopCrush about prepping for the complex part and overcoming what could have been a seriously awkward moment on set! She even gave behind-the-scenes details about an entirely different role -- yes, a mermaid -- for her Project Mermaids shoot.

On ‘Baby Daddy,’ you play Riley’s frenemy, Heather. Can you talk a little bit more about the character?

Heather is Riley’s frenemy from summer camp back in the day, and she was that annoying girl that always had to one-up Riley in everything. She comes back years and years later, and Riley’s so excited because she really has her life together and she’s a young attorney, and Heather comes back in the picture and once again is just one-upping her in everything and just stirring up a ton of drama for her and gets in between her and her relationship with the boys. I basically come in to make her life hell for a little bit [laughs].

A frenemy is kind of a mix between the good person, but with a little bit of that villainous edge. How did you go about preparing for that? 

It’s fun because it’s almost like playing a mean person with a smile on your face. Very passive aggressive, that is definitely how I would describe Heather. She’s almost like one of those girls that says something really cruel, but has a smile on her face so you can’t really say anything. You’re just like, “Wait, hold on a second… Oh, wow, she just completely dissed me.” It’s walking this line of making somebody feel inferior to you, yet still being snarky and catty at the same time.

Will we get to see a sweeter side of Heather as well?

Yes, I mean, I don’t want to give anything away, but she does come around a little bit and at the end of the day, she’s one of those girls that I think doesn’t even realize how much she’s messing up Riley’s life. You know, there’s a part of her that just naturally enjoys it, but there’s another part that doesn’t even realize that she’s doing these things. She’s just one of those characters and she’s not 100 percent trying to be this awful person, it’s just that she’s one of those girls who’s naturally just like a little better in everything. I know that sounds really terrible, but I don’t know how else to explain it. The writers did a really good job of keeping her in this happy medium where she’ll say something kind of nice and then she’ll just completely ruin it.

Did I read correctly that you’re going to be on ‘Baby Daddy’ for multiple episodes?

Yeah, it’s going to be two episodes. I don’t know about anything for the future.

Is there one really funny behind-the-scenes moment from on set that you sticks out to you?

It’s so hard because I feel like it was like the entire two weeks I was there was just pure fun and laughter and everybody was just so welcoming. I honestly had the best time. We laughed so much. I can’t think of one specific thing, but I do know that the first day, you know you come into a table read for a half hour. I went in for the table read on a Monday and I had been semi-recovering from an awful case of food poisoning, to be completely honest, from the night before. Like, one of the sickest I’ve ever been in my entire life.

So it was terrible, but it was kind of comedic that it was like the first day and I just walked in like looking and feeling like hell, having to meet this new cast. Looking back, it’s just so ridiculous, but they were all so sweet. I mean, the set medic was coming to me, “Do you need crackers?” and Chelsea [Kane] was like, “Should we make you tea?”

It was really awful at the time, but when I look back I’m kind of like “Um, of course.” Sort of ironic, the guest star comes in completely sick. You know, if it’s your own show, you see these people every day, but I’m like, “Oh, this is so embarrassing. I have to meet them with sweat pellets dripping down my forehead, feeling awful and trying to rid this sickness." So that’s my humor. I kind of found that funny.

It turned out well, which is why it’s funny.

Exactly! It went away quickly.

Switching gears, I saw you posted a picture and video on Instagram from your Project Mermaids shoot. Can you talk a little bit about the transformation into a mermaid?

Oh, yeah! Anything that’s charity-based, if a friend asked me to be a part of it, I’m like, “100 percent yes” or if I just see something and I’m like, “Oh, that’s interesting” and charity-related, it’s like always a yes. Charity is a big part of what I do as well, so I love the fact that one, I got be a mermaid and two, help save our beaches.

I was incredibly drawn to the project, and it was really fun. It was actually way more difficult than it looks. Getting that tail on -- it’s like a 20 lb. tail, I swear – it’s pretty intense. They were like, “You were the only mermaid we’ve had to shoot in the rain” and I was like, “OK, cool, just my luck. That’s great.” So it was freezing outside, I was shivering and they shot me in the woods, so we had to walk down this mountain, no joke. We did it at TreePeople up in Cold Water Canyon, so it was one of those moments. It was raining. I don’t know why I decided to wear booties. I didn’t know we were going to be, like, mountain climbing, but I had to take off my heels. I was getting pricked in the feet by all these rocks, but it kind of got me into the character. I was like, “Guys, if a mermaid was really trying to escape the ocean, I feel like she would go through with these things.” But we had a lot of fun. We just laughed it off.

They basically take baby oil and just drench your entire lower half, your legs and everything. It takes two people to lift you into this tail, and another person to pull the tail up and then they slowly sit you down onto a yoga mat in the woods and we were on a complete arch, so if they let go, I was gone. It was like, “sayonara” because I had no feet at this point, just a tail. But once it was on and once it was comfortable and whatnot, it was so much fun. It’s just so weird looking down at your body and not having feet. I feel like it’s oddly every girl’s dream, so I had a blast.

And then I got to go in the water, and that was actually really hard because it slips down. There’s nothing that holds you in, so it’s a little bit difficult, but once I got the hang of it, they were laughing. They were like, “You are the only person who once we said that we’re done, just wants to keep going.” I was like “Wait! Can I just do one more flip? Can I try this?” Nevermind that it felt like I got hit by a train the next day. It was the hardest workout of my life. I had the best time. I loved being a mermaid and I got to fulfill my childhood dream.

Was it hard swimming with a mermaid tail?

It was! It was actually really difficult. I found my own little niche and I got used to it and I figured out how to pull it up myself, but in the beginning it was really difficult. It’s scary because it’s so heavy and you don’t have your feet, you only have your arms. If you tip over, I was scared I was going to drown. “How do I get up? I don’t have my feet to flip around?” But you kind of get the hang of it and you have to really use your arms. Like I said, it was the best workout of my life and once I got the hang of it, it was much easier and really fun. It was way harder that I thought at first. They were saying that all of the girls, the ones that decided to do the water, found it to be extremely difficult, but like I said, I got really into it. Of course, I’m like, “Wait, no! One more hour!”

Did you watch get to research by watching 'The Little Mermaid'? 

I’ve watched 'The Little Mermaid' probably 3,000 times in my entire life, so I didn’t have to watch it prior. But I love Disney movies and I love Disney princesses. I mean, Ariel is kind of princess, right?