This paper explores the profound cognitive and affective impacts of Large Language Models (LLMs) and Generative AI (GenAI) on human thought, imagination, and especially our emotional life by analysing our interaction with different styles of GenAI agents especially when presented as virtual personalities. I describe how LLL-based agents can be presented using one of three broad metaphors of interaction, namely as Assistants, Extenders and Companions. Each metaphor of interaction implies distinctive cognitive patterns for their human interactant. I explore especially the shape of some current interactions with GenAI companions and analyse their roles as cognitive and affective mind shapers. I analyse how Companion AI agents based on LLM technology can come to be treated as ‘Ersatz Others’ taking up deep roles in our cognitive and affective lives. I explore some of the perhaps unexpected implications of the deep reliance on such systems especially from the point of view of the theory of the extended mind and the mind-technology problem and show how this new sort of cognitive and affective environment for the human mind produces some new ethical challenges and may even reshape our future understandings of what minds are.