Returning characters?

Caitlin Blackwood who played young amelia pond in last years series of Dr who will be returning again as young Amelia Pond in Episode Thirteen, but she won’t be the only member of the TARDIS team to return She will also be joined by Ezekiel Wigglesworth as young Rory.

Also Nina Toussaint-White’s character Mels also has a younger version of herself in the episode played by Maya Glace-Green.

Source - Dr who spoilers