Complex sentence: Stanley "Stan" Porter is a fictional character in a special episode of the popular BBC soap opera "EastEnders", played by Sam Kelly in the episode,', but played by Callum Dixon in flashbacks within the episode.
Split into simpler sentences: Stanley "Stan" Porter was a fictional character in a special episode of the popular BBC soap opera "EastEnders". He was played by Sam Kelly in the episode,', but played by Callum Dixon in flashbacks within the episode.