This work aims to describe and analyze a relatively new, puzzling construction that has become very productive in informal registers of English. It is primarily used by younger generations, especially on the web and social-media platforms, but also in spoken language. It appears with the configuration negative marker + subject in the accusative case + gerund (e.g. Not me taking the train at 5 a.m.; meaning: it is ironic and unexpected that I took the train early at 5 a.m.). These constructions, which we dubbed not-ACC-ing constructions, are strictly root phenomena where negation does not reverse the polarity of the sentence. They convey a peculiar ironic, sarcastic, self-deprecating flavor. The existence of the not-ACC-ing construction raises the following questions, which we will address in this article: (i) How come negation does not have its prototypical function of reversing the polarity of the sentence? (ii) How come the subject is in the accusative case, despite not-ACC-ing constructions being invariably root? (iii) How is their peculiar interpretation obtained? We propose an analysis that captures all their structural and interpretive properties by combining some crucial ingredients of Lowe’s (2019) analysis of ACC-ing constructions and Greco’s (2020) analysis of Expletive Negation.