Houdini & Doyle (2016)

S1E20 Best Prom Ever

Title: Ultimate Prom Experience Plot: Lily, Barney, and Robin head to a high school prom to check out a possible band for Lily and Marshall's upcoming wedding. To gain entry, Lily and Robin pose as the dates of two students who planned to attend solo. Meanwhile, Ted and Marshall stay at their apartment, busy putting together the wedding invitations for distribution.