On the Doctor Who 50th Anniversary there were three Doctors, one companion and a companion-ish, PLUS every other Doctor at least in appearance to help save the "Day of The Doctor."
On Doctor Who Season 7 Episode 14, "The Name of the Doctor," Madame Vastra orchestrated a conference call on which River Song and Clara met for the first time.
On Doctor Who Season 7 Episode 12, "The Crimson Horror," featured Diana Rigg in a guest role as Madam Vastra, Jenny and Strax helped save the people of Sweetsville.