
Charles Peckham Day (born February 9, 1976) is an American actor, writer, and producer. He is best known for playing Charlie Kelly on the FX/FXX dark comedy It's Always Sunny in Philadelphia (2005–present), of which he is also a writer and an executive producer. In 2011, he was nominated for a Critics' Choice Television Award and a Satellite Award for the role. Subsequently, he co-created the Apple TV+ comedy Mythic Quest (2020–2025) with Rob Mac and Megan Ganz.
In film, Day is best known for his performances as Dr. Newton Geiszler in Guillermo del Toro's Pacific Rim (2013), Dale Arbus in the comedy Horrible Bosses (2011) and its sequel Horrible Bosses 2 (2014), and Andy Campbell in the comedy Fist Fight (2017). He is also known for his voice roles in Monsters University (2013), The Lego Movie film franchise (2014–2019) and Nintendo franchise character Luigi in The Super Mario Bros. Movie (2023) and its sequel, The Super Mario Galaxy Movie (2026). He made his directorial debut with Fool's Paradise (2023).
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The Super Mario Galaxy Movie
2026 · as Luigi (voice)

The Super Mario Bros. Movie
2023 · as Luigi (voice)

Pacific Rim
2013 · as Dr. Newton Geiszler

Pacific Rim: Uprising
2018 · as Dr. Newton Geiszler

Monsters University
2013 · as Art (voice)

The Lego Movie
2014 · as Benny (voice)

Vacation
2015 · as Chad

The Lego Movie 2: The Second Part
2019 · as Benny (voice)

Horrible Bosses
2011 · as Dale Arbus

Horrible Bosses 2
2014 · as Dale Arbus

Honey Don't!
2025 · as Marty Metakawitch

Wildwood
2026 · as Seamus (voice)

Hotel Artemis
2018 · as Acapulco

Fist Fight
2017 · as Andy Campbell

Party Central
2014 · as Art (voice)

Going the Distance
2010 · as Dan Grant

Summer of 69
2025 · as Rick Richards

Fool's Paradise
2023 · as Latte Pronto