A | Apartment Roller Luge
The game Robin invents to console Lily and Marshall over the slanted floors in their new apartment. Equipment needed: a skateboard, a metal salad strainer, and an open doorway.
B | Blue French Horn
The instrument hanging in the restaurant where Robin and Ted have their first date. ''That horn is the pilot to me,'' says Smulders. ''We haven't made reference to it in so long. It's a Horcrux of the show.'' (For you non-Potter geeks, that means it's, like, super-important.) Now hangs in co-creator Craig Thomas' office.
C | Cockamouse
The flying mouse/cockroach hybrid that sets up shop in the gang's apartment. Also one of Segel's favorite episodes: ''The episode makes me laugh like crazy,'' he says. ''We got to shoot it like it was a horror movie and overact, which I love.''
D | Doppelgängers
Each of the gang has a ''twin'' revealed over seasons 5 and 6. Stripper Lily, Lesbian Robin, Señor Justicia (a mustachioed Marshall), Mexican Wrestler Ted, and Dr. John Stangel (Lily's fertility doctor, who's a ringer for Barney with a beard). Also the subject of Smulders' fantasy episode: ''I wish we could do an episode that is just the doppelgängers. Their lives would intersect as well. That's the show I want to watch!''
E | Eighty-Three
The number Barney always uses when inventing a statistic. Example: ''There is an 83 percent correlation between the times men wear boutonnieres and the times they get laid.''
F | Fiero
Marshall's beloved Pontiac, which ends up in the Big Parking Lot in the Sky when it conks out just shy of 200,000 miles. A Cassingle of the Proclaimers' ''I'm Gonna Be (500 Miles)'' is stuck in the tape deck. ''I love that you have all these flashbacks that fill in the blanks...which tell how everyone met everyone,'' says Radnor of the episode, which is one of his favorites. ''There's something so sweet and hilarious about that.''
G | Gary Blauman
Barney's colleague played by Smulders' real-life husband, Taran Killam. Blauman makes a public show of quitting his job by trying to pee on the conference table during a meeting. (Damn, pee shyness!) According to Barney, Blauman lost all his money soon after. ''Then he became a janitor at an old folks' home and moved into a one-room apartment above a bowling alley.... He died.'' Problem is that Blauman pops up again very alive in subsequent seasons. (And rumor has it that he'll show up in season 9.) A side note: Most of the cast's significant others have guest-starred on the series during its run: David Burtka, Harris' partner, recurs as Lily's high school boyfriend Scooter, and Hannigan's husband, Alexis Denisof, appears as Robin's co-worker, blowhard newscaster Sandy Rivers.