Jimmy Williams, played by Darcy Tadich, made his first screen appearance on 10 June 2015.[14][15] The character and casting was announced on 17 May 2015.[14] The role marks Tadich's television acting debut.[14] Jimmy is the young son of returning character Amy Williams (Zoe Cramond) and the first grandchild of established regular Paul Robinson (Stefan Dennis).[14] Paul was unaware of Jimmy's existence due to his estrangement from Amy, but was "overjoyed" to learn that he had a grandson.[16] Jimmy and Paul got along well, but Amy was aware of how "impressionable" Jimmy was and became concerned that Paul might overindulge her son.[16]
After Amy's cousin Daniel (Tim Phillipps) asks her to return to Erinsborough to reconnect with Paul, she agrees for Jimmy's sake. Jimmy meets his grandfather for the first time and enjoys his stories of an old well nearby. He later disappears from Sonya Rebecchi's (Eve Morey) garden and Amy suspects he has gone down the well. However, Jimmy goes to The Waterhole looking for Paul and he bonds with Naomi Canning (Morgana O'Reilly), Paul's assistant. Amy allows Paul to look after Jimmy while she is working. Paul connects with Jimmy and buys him expensive presents, which Amy later returns to him, having previously mentioned that Jimmy could not have them until Christmas. When Jimmy struggles with his science project, he calls Paul for help. Amy returns home to find them working together and is impressed that Paul did not need to spend money on Jimmy to help them bond. Jimmy finds a bag of letters that contain the secrets of the residents of Ramsay Street. He reads a couple and blackmails Karl Kennedy (Alan Fletcher) into giving him a cake. He later tries the same thing with Karl's wife Susan (Jackie Woodburne), but she marches him home to Sonya, who then tells Amy. Jimmy is reprimanded, but when he finds Sheila Canning's (Colette Mann) secret, he blackmails her into giving him crisps and cake. When Sheila cannot cope with the pressure, she shakes Jimmy. His cries attract Amy's attention and Sheila admits that he has been blackmailing her. Jimmy's father Liam returns, and they spend time together. Amy allows Jimmy to walk to a Dial-a-Kyle, but he goes missing after encountering Sam Mako, a criminal with whom Liam had dealings. Stephanie Scully (Carla Bonner) finds him hiding at school and he is reunited with Amy. He later witnesses his father accepting a bribe from Paul never to contact him or Amy again, after which Jimmy becomes distant from Paul. Jimmy does not like Kyle taking the place of Liam until he is told of his father's crimes. Mark takes Jimmy on a tour of the police station where he steals pepper spray and later sprays it in Charlie's face. Charlie requires medical treatment. While Jimmy and Charlie are playing with a drone, it flies off and Jimmy gets on his bike to catch up to it. He is struck by a car and the driver leaves the scene. Jimmy is rushed to the hospital, where he has to undergo surgery to remove a ruptured spleen.