Soon there will be sex robots. The creation of such devices raises a host of social, legal and ethical questions. In this article, I focus in on one of them. What if these sex robots are deliberately designed and used to replicate acts of rape and child sexual abuse? Should the creation and use of such robots be criminalised, even if no person is harmed by the acts performed? I offer an argument for thinking that they should be. The argument consists of two premises. The first claims that it can be a proper object of the criminal law to regulate wrongful conduct with no extrinsically harmful effects on others. The second claims that the use of robots that replicate acts of rape and child sexual abuse would be wrongful, even if such usage had no extrinsically harmful effects on others. I defend both premises of this argument and consider its implications for the criminal law. I do not offer a conclusive argument for criminalisation, nor would I wish to be interpreted as doing so; instead, I offer a tentative argument and a framework for future debate. This framework may also lead one to question the proposed rationales for criminalisation.