Marlo Buchanan

Dr. Marlo Buchanan is a recurring character in the Barbie franchise.

Story
Dr. Buchanan debuted in the movie Barbie: Dolphin Magic as Ken's boss at his summer job, a marine biology facility. She was pretending to be a qualified marine biologist who was preserving the magical Gemstone Dolphins, brightly colored dolphins that were extremely rare. She eventually revealed she was actually a poacher who was planning on using them to get millions of dollars. In the movie Mermaid Power, Marlo comes back, this time as a qualified marine biologist working for Dr. Ivy Tang, who she is desperate to impress with her discovery of the dolphins as well as mermaids (as she met Isla, Barbie's mermaid friend from Dolphin Magic). She goes out to find more mermaids, and encounters Barbie, her sisters, and her new friend Brooklyn. She later, seemingly still evil, captures a mermaidified Chelsea and her friend Aquaryah Aquavilla, and traps them in a tank in her submarine. Barbie, convinced she's a villain (even though she wasn't kidnapping out of malice, as she explains), goes to find the two girls and confronts Marlo, who explains what she was actually doing. Unfortunately, the sub gets flooded and starts to sink, and Marlo passes out in panic, about to drown. Barbie then saves her by putting her magical necklace on Marlo. Marlo comes back to and is transformed into a mermaid to her delight, and it's revealed that she could turn into a mermaid because Grandma Buchanan, her grandmother, was actually a mermaid herself.