| Issue | #21 |
| Published | November 2007 |
| Cover Price | 2.99 USD; 3.65 CAD |
| Pages | 36 |
| Editing | Matt Idelson; Nachie Castro (associate) |
| Notes | This issue went on sale 2007-09-05 (non-US) and 2007-09-06 (US) (on time). This issue is labeled as a Countdown Tie-in. |
| Characters | Supergirl; Karate Kid (Lightning Saga) |
| Genre | Superhero |
| Pencils | Bernard Chang |
| Inks | Bernard Chang |
| Letters | typeset |
| Notes | This issue went on sale 2007-09-05 (non-US) and 2007-09-06 (US) (on time). This issue is labeled as a Countdown Tie-in. |
| Characters | Supergirl [Kara Zor-El]; Jonathan Kent; Martha Kent; Karate Kid (Lightning Saga); Una [Triplicate Girl]; Karate Kid (current, cameo); Triplicate Girl (current, cameo); Mister Orr; Equus; Wonder Girl [Cassie Sandsmark] (cameo); Robin [Tim Drake] (cameo); Miss Martian (cameo); Kid Devil (cameo) |
| Synopsis | Kara visits the Kents to seek comfort after wrecking Air Force One. Karate Kid and Una hitch a ride on a train heading for Colorado to seek out Buddy Blank. Equus calls in a train derailment to the government to set up Karate Kid and Una, and then causes it. Supergirl responds, and flies Karate Kid off, but doesn't recognize him or Una. After mentioning the Legion of Super-Heroes, Supergirl suddenly remembers the group she was a part of (which included different versions of these two Legionnaires), but collapses from the sudden rush of memories. But in the meantime, Equus brings the fight to them. |
| Genre | Superhero |
| Script | Tony Bedard |
| Pencils | Renato Guedes |
| Inks | Jose Wilson Magalhaes |
| Colors | Renato Guedes |
| Letters | Jared K. Fletcher |
| Notes | Story continued from events in Countdown (2007 series) (taking place between issues 34 and 31), and continues in the next issue. |
| Script | Dan Didio |
| Notes | Dan talks about the end of convention season, and a summary of new books and artists announced at them. Ads for Supergirl #22, Black Canary Wedding Planner #1, Countdown #34, and Infinity Inc. #1. Appears on page 34 in this issue. |
| Notes | House ads for: Wonder Woman: Love and Murder hardcover (1/2 page), Green Arrow/Black Canary Wedding Special, Countdown to Adventure, Suicide Squad: Raise the Flag, Justice Society of America: The Next Age hardcover, Infinity Inc., Tales of the Sinestro Corps one shots, and Countdown to Mystery. Appear in various places in this issue. |
| Notes | Total of 4 one-page and 1 half-page ads for: got milk? with Masi Oka (milk), abovetheinfluence (Partnership for a Drug-Free America), Dragonball Z Season 3 (DVD, Funimation Entertainment, 1/2 page), Alien Syndrome (video game, Sega), and Comic Collector Live (collection software, Midten Media). Appear in various places in this issue. |