The 2010 TV series Pair of Kings follows the misadventures of twin brothers Brady and Boomer (at least, in the first season) who discover that they're the heirs to the throne of the fantastical island kingdom of Kinkow. They move from their home in Chicago to the island, where they rule as its pair of kings and learn to be worthy of the responsibilities that come along with the role.
In a season 1 episode, Brady and Boomer encounter mermaids. Namely, five beautiful young mermaids by the names of Aerosol, Amazonia, Amnesia, Ammonia, and Onomatopoeia (TRULY). The mermaids are friendly at first, and Aerosol (Leslie-Ann Huff), their leader, explains how they badly desire human legs, but can only gain them if the king of Kinkow carries them over the threshold of the palace. What luck, say Brady and Boomer, for they are the kings of Kinkow!
The twin kings carry their new friends over the threshold into the palace, but once the mermaids have gained legs, they reveal their true agenda and kick the kings out. They're there for a hostile takeover, and it's a good thing they have some mermaid powers to help them with this. Mikayla, who is assigned security detail for the day, tries to kick the mermaids out but ends up being transformed into a mermaid herself. But all's well that ends well when the twins discover the mermaids' weakness: salt water, which turns their legs back into tails.