Olivia Olson is an American actress, singer-songwriter, and screenwriter, recognized for her prominent voice roles. She lent her voice to Vanessa Doofenshmirtz in "Phineas and Ferb" and Marceline the Vampire Queen in "Adventure Time." Her acting career also includes a role as Joanna in the film "Love Actually" and its sequel. Beyond her performance work, Olson has expanded into writing, contributing to graphic novels and books related to "Adventure Time," and is also involved in the "Phineas and Ferb" revival as a writer.

Olson was adopted at birth and raised in Los Angeles. Her career began with acting and singing roles on television and in live theatre. Her performance in "Love Actually" at a young age garnered attention, leading to further television appearances. She has since released her own music, including an EP and an album, and maintains a presence on social media platforms. Her work on "Adventure Time" was particularly impactful, with her character Marceline becoming a fan favorite and contributing to the show's critical and commercial success.

Olivia Olson is widely recognized for her voice acting, most notably as Vanessa Doofenshmirtz in the animated series "Phineas and Ferb" (2008–2015) and as Marceline the Vampire Queen in "Adventure Time" (2010–2018). In her role as Vanessa, she performed numerous songs for the show, some of which she also wrote. Her portrayal of Marceline led to significant critical acclaim and fan popularity, with the character becoming a fan favorite. Olson also sang Marceline's songs, contributing to the show's musical landscape, and notably performed the song "Everything Stays" in the "Stakes" mini-series. Her father, Martin Olson, also contributed to both "Phineas and Ferb" and "Adventure Time" as a writer and voice actor, respectively.

Beyond her performance career, Olivia Olson has established herself as a writer. She co-authored the Boom! Studios graphic novel "Marcy and Simon" and collaborated on "Adventure Time: The Enchiridion & Marcy's Super Secret Scrapbook" with her father. She also contributed to the best-selling "Adventure Time Encyclopedia" for Cartoon Network. In 2023, she began writing for the "Phineas and Ferb" revival, continuing her involvement with the franchise in a new capacity. Her writing contributions demonstrate an engagement with the narratives and characters she has helped bring to life.

Olson gained early mainstream recognition for her role as Joanna in the 2003 film "Love Actually," where her singing of "All I Want for Christmas Is You" was praised for its authenticity. This early success led to guest appearances on television shows and opportunities to sing with notable artists. In addition to her acting and voice work, Olson has pursued a solo music career, releasing her debut EP "Beauty Is Chaos" in 2013 and the album "Nowhere Land" in 2018. She has shared original music on her YouTube and TikTok accounts, showcasing her multifaceted artistic talents.

“she and Sangster talked "about the whole Ferb-Vanessa situation 'cause it's pretty funny."”

“she was "honored" to be voicing a character in a show pushing the limits, including on "what a female character in a TV series brings to the table."”