Complex sentence: The Doctor, while confused about his new look, recalls how it appears similar to another that he's seen; the Tenth Doctor met a man named Caecilius in "The Fires of Pompeii", played by Capaldi.
Split into simpler sentences: The Doctor, while confused about his new look, recalls how it appears similar to another that he's seen. The Tenth Doctor met a man named Caecilius in "The Fires of Pompeii", played by Capaldi.