The Chronicles of Tri

The Chronicles of Tri is a British teen sci-fi drama that airs on BBC One and CBBC in the UK. It is a spin-off of the televisions series Doctor Who and focuses on The Doctor's grandchild and sibling of former companion Susan, Tri, who, like their grandfather, can regenerate. Tri was initially portrayed by Asa Butterfield for the first 5 series, before regenerating into Isobelle Malloy. When in their first incarnation, Tri referred to his name as short for 'Dimitri', but when in her second incarnation, Tri reveals it's now short for 'Yekatarina'. The show has aired 9 series to date with a total of 108 episodes, made up of 54 two-part stories.