doyle

They've done one episode when a mid-1980's Brigadier met up with a late-1970's Brigadier (I don't recall exactly what happened, except that the timetravel pseudoscience caused a giant energy discharge when they touched, and the 70's Brig ended up with amnesia), and several where the Doctor met a previous regeneration of himself (which you probably knew already.)

I really shouldn't be reading your Dr. Who posts, we're two weeks behind you here...