In Doctor Who, Nerys was a minor character encountered during the 10th Doctor’s escapades alongside Donna Noble. The reference to Nerys in ‘The Star Beast’ serves as a means for the Doctor to explain his familiarity with Donna, as he cautiously navigates evading any potential recollection of their shared adventures by Donna.
Throughout their interactions, it’s implied that Nerys and Donna had a complex relationship characterized by a mix of friendship and antagonism. Their dynamic was often marked by an interplay of love and resentment, with Nerys perceiving Donna as someone always seeking attention, while Donna believed Nerys harbored intentions to undermine her. Notably, Nerys was present at both of Donna’s weddings, prompting Donna to suspect Nerys of having ulterior motives, hence her depiction of Nerys as a ‘viper in the nest.’
Ultimately, the mention of Nerys within ‘The Star Beast’ primarily serves as an Easter egg for dedicated Doctor Who enthusiasts. However, it also serves to establish a subtle link to Donna’s past adventures, reinforcing her enduring connection as the beloved Doctor Who companion fans have come to know and cherish.