The Party is based on a concept by the author Lucy Hawking and is written by Sumita Majumdar, who drew on her own experiences as a person with autism in similar social situations. Throughout the film, viewers hear Layla’s thoughts, voiced by the autistic teenager Honey Jones. The storyline was developed after extensive focus groups and interviews with people on the autism spectrum as well as with input from the National Autistic Society, the Autism Research Trust and the University of Cambridge Autism Research Centre.
The visual and auditory effects in the film were based on scientific research about the kinds of symptoms seen in autistic individuals, such as difficulties with processing faces, and hypersensitivity to lights, loud noises and strong odours. Interviews conducted with autistic women also revealed they had issues with how things sound during a meltdown, including having difficulties distinguishing between sounds, hearing echoing voices and being unable to process the other information around them.