The Summer I Turned Pretty isn't ending quite yet thanks to a surprise movie. Based on Jenny Han's book series, Prime Video's adaptation followed the love triangle between Belly (Lola Tung) and the Fisher brothers: Conrad (Chris Briney) and Jeremiah (Gavin Casalegno). The Summer I Turned Pretty, It's Not Summer Without You and We'll Always Have Summer served as inspiration for the show's three seasons. While viewers were expecting the series to wrap up after season 3, Han had a surprise up her sleeve.