Sean Ackard is Hanna's ex-boyfriend and the son of a minister and a dentist.
Hanna had a crush on him since 7th Grade, which Alison constantly taunted her about.
Sean was originally Hanna's crush before Alison disappeared, back when Hanna was still "Hefty Hanna." They began dating at some point after Alison's disappearance.
Sean is seen walking up to Hanna and Mona with Noel.They tells the girls that Noel's parents are going to be out of down so the biggest party of the year is officially on. Later, Hanna flashbacks to the time in her chubby days when she asked Sean out to a party; he had accepted along with added pressure from Alison.