Peter Bretter is a fictional character from the romantic comedy film Forgetting Sarah Marshall. He is portrayed by actor Jason Segel, who also co-wrote the film. Peter is a struggling musician who experiences heartbreak after his girlfriend, Sarah Marshall, played by Kristen Bell, breaks up with him. Throughout the film, Peter embarks on a journey of self-discovery while vacationing in Hawaii. He encounters various characters, including Rachel, played by Mila Kunis, who helps him heal and find new love. The story explores themes of love, loss, and personal growth.