Erica and Brianna are two girls who are guests at Surfer's Paradise. They are basically the female versions of Mark and Todd Marvin, as they cause trouble (though not to the extent that Todd and Mark do) and blackmail Lo.
- Brianna is older than Erica.
- Brianna looks like a smaller, younger version of Lo with shorter and lighter color hair.
- Brianna was not supposed to spend any money, according to her mom, so she can save money.
- Erica wasn't supposed to eat sugary and fried foods, because she was on a diet.
- Both then took surfing lessons alongside Mark and Todd from Lo at the end of "Reef And That Evil Totem".
- Erica is voiced by Rachel Marcus.
- They were blackmailed (alongside Mark and Todd Marvin) by Lo into cleaning guest rooms in "Boards of Glory" as punishment for sending the girls' mom's dog out to sea on a surfboard, surrounded by sharks. They later called child services in retaliation.
- They were at the Captain Ron promo at the Surf Shack.
- Lo was starting to like Brianna.
- Brianna (only) made a cameo appearance in "Channel Surfers."
- Their mom appears to be a single parent, since Erica and Brianna's dad isn't seen or mentioned and in Reef And That Evil Totem, when Johnny gathered up the kids' parents, it just Erica and Brianna's mom along with Mr. and Mrs. Marvin.
- Reef And That Evil Totem (debut)
- Boards of Glory
- Who Knows What Evil Lurks in the Heart of Clam? (cameo)
- Endless Bummer
- A Prank Too Far (cameo)
- Surf Surf Revolution (Brianna only, cameo)
- Will the Real Broseph Please Stand Up (cameo)
- Channel Surfers (Brianna only, cameo)
- Hunka Hunka Burning Reef
- Surfer's Got Talent (cameo)