The flashbacks laid out a standoff between Ted (Josh Radnor) and Marshall (Jason Segel) over whether Ted actually got Marshall and Lily (Alyson Hannigan) a wedding gift, and whether they in turn sent him a thank-you note. Each guy passive-aggressively tried to make his point by dropping hints that sailed right over the other’s head.
It culminated at one of the gang’s rooftop Halloween parties, with Marshall dressing up as a wedding present and Ted going as a thank-you note (the only time, incidentally, we’ve ever seen him not dressing as an out-of-date hanging chad). As the scene ended, Ted walked out of the frame to reveal … Katie Holmes as the Slutty Pumpkin, reprising her role from a couple seasons ago (the photo above is from that episode).
That was it — Holmes didn’t have any lines, and it was almost literally a blink-and-you-missed-it moment. But it was a nice little callback to the show’s past, and now we know why she and Ted didn’t meet up that year — she was looking for a hanging chad, and Ted didn’t oblige.