Graduate teaching assistants (GTAs) have been described as being "neither fish nor fowl," occupying a role between student and teacher. Their multiple identities are commonly framed within the literature as a key challenge. This study explored the perspectives of GTAs when discussing their teaching work, through activity-oriented focus groups with nine GTAs from a UK university. Thematic analysis revealed that whilst GTAs showed a lack of clarity over their identity, they are actively involved in the process of "identity work" through negotiating an emerging professional identity. Furthermore, liminality of status, being neither fully a student nor teacher, allows GTAs to operate with identity malleability, adjusting their most salient identity to meet the demands of the situation. It is argued that rather than occupying an "ambiguous niche," GTAs occupy a "unique niche" and the identity malleability they possess affords the optimum conditions in which to engage in identity work.