We see Wilf, who is officially the Tenth Doctor's last Companion, his grand-daughter and former Companion Donna, her mother Sylvia, The Master, as well as brand new characters. We also have our fist pictures of actress Sinead Keenan who also appears in the specials in the role of Addams, a green spiky alien. I interviewed Miss Keenan a few months back and you can read it here.
Go here, here and here to see the pictures.
There is also a brand new clip of the episode which you can view here. The clip starts 25 seconds in.