TV Watch 'HIMYM' Welcome Another 'Liar' By Jarett Wieselman 12:53 PM PST, January 18, 2013 In 2007, Lucy Hale played Robin's little sister, Katie Scherbatsky, in an episode of How I Met Your Mother, titled First Time in New York and on Monday, another one of ABC Family's Pretty Little Liars heads on over to CBS' hit comedy. RELATED - HIMYM Creator Previews What's To Come In Ring Up, Ashley Benson plays a much (much!) younger girl Ted has started dating ... one whose date and word choices constantly remind him just how old he actually is. RELATED - Lindsey Shaw Opens Up About Dark PLL Days Watch ETonline's exclusive sneak peek of Benson on HIMYM and use the comments to guess which girl (Troian Bellisario, Shay Mitchell) will stop by MacLaren's next, making it a PLL hat trick! How I Met Your Mother airs Mondays at 8 p.m. on CBS.