Complex sentence: The teen girl screams as a small seemingly harmless spider crawls across the carpet which prompts the teen boy to get off the couch, that they are sitting on, and pick up the spider only to be violently thrown about by the spider.
Split into simpler sentences: The teen girl screams as a small seemingly harmless spider crawls across the carpet. This prompts the teen boy to get off the couch that they are sitting on and pick up the spider, only to be violently thrown about by the spider.