Crispin was a cleric who served with the investigation of the crash of the Byzantium. (TV: The Time of Angels). He was left to help protect Amy Pond with three other clerics, then was sent to investigate the mysterious light with another cleric. He was absorbed by the Time Field crack and forgotten with his companions. (TV: Flesh and Stone)
Before Rory Williams was erased by a time field, Amy remembered that she could still remember the clerics, even though they could not remember each other. (TV: Cold Blood)