A native of Vestavia Hills, Alabama, McCullers attended Indian Springs School which is a private high school in Indian Springs Village, Alabama.
McCullers began his career as a writer for Saturday Night Live.
[3] He wrote the 2017 film The Boss Baby for DreamWorks Animation, and with Genndy Tartakovsky co-wrote Hotel Transylvania 3: Summer Vacation (2018) for Sony Pictures Animation.
[4] In 2023, he was brought on to write material for the film Ruby Gillman, Teenage Kraken.
[5] McCullers lives in Los Angeles[6] with his wife and four children.