OVA

My Gurren is Sparkling!! (俺のグレンはピッカピカ!!) is short ten-minute OVA bundled with the Nintendo DS game based on the series. It was made from a failed script for the show and is sometimes referred to as Episode 5.5.

Synopsis
As Team Gurren rests in a canyon, Tetori (ティトリ) --a young cat-like beastgirl-- sneaks up on a sleeping Kamina and uses a permanent marker to black out his sunglasses. When Kamina wakes up, he immediately assumes himself to be blind and makes a huge fuss until an annoyed Yoko pulls off his sunglasses. Tetori then impresses Kamina by polishing his shades to a mirror-shine with a quick spray of her special cleaning solution. She then volunteers to clean the rather grimy Gurren. Jealous of Lagann's shine (which is thanks to Simon's tireless work), Kamina grants her permission. But just as Tetori engulfs Gurren in lather, an enemy Gunman comes flying into the canyon. Kamina and Yoko join Simon in Lagann in order to chase the Gunman down, but rather than fighting the Gunman begins running in the opposite direction.

Lagann gives chase, but the trio soon become concerned that they might be running right into a trap. Just as they decide to turn back, Lagann is attacked from behind by a surprisingly clean Gurren. It seems that Tetori set them up in order to allow her partner-in-crime, Ziggitalis (ジギタリス) to steal Gurren. Simon attempts to unite Lagann with Gurren in order to take it back, but Ziggitalis produces a Gunmen-sized baseball bat and knocks Lagann away. Angered by the theft of his mecha, Kamina jumps out of Lagann intending to take Gurren back with his own two hands, but promptly falls of a cliff instead. Before Simon and Yoko can rescue him, Ziggitalis' counterattack forces them to back off. Fortunately, Kamina saves himself by embedding his sword in the cliff wall, and when he climbs back up, he discovers an abandoned rabbit-like Gunman.

Meanwhile, Simon finds himself outclassed by Gurren and the other Gunman, but is suddenly rescued by Kamina and his new Gunman, which he names Usappyon (ウサピョン) (to Ziggitalis' annoyance). Kamina knocks Gurren away and tells Simon to unite with Usappyon-- an idea Simon isn't terribly fond of. Nonetheless, Kamina has his way, and Usappyon-Lagann is born. Despite its lack of arms, Usappyon-Lagann is able to deliver a stunning blow to Gurren, giving Simon the chance he needed to abandon Usappyon and re-unite with Gurren. Having lost control of Gurren, Ziggitalis abandons the mech and runs for Usappyon, while Kamina jumps back into Gurren. However, Ziggitalis is saved when Tetori enters the scene with a Gunmen of her own, Megaheadz (メガヘッズ) and combines with Zaolegg (ザウレッグ), allowing them to escape unharmed.

Trivia

 * After the credits, the message “SECRET CODE 17 70 71 72 75 76” appears. When the skills with the corresponding numbers are equipped in the NDS game, a short scene plays where the secret skill "Gurren Homerun" (in which Gurren hits Lagann with a baseball bat, as in the OVA) becomes unlocked.
 * In the original Nyoro~n Subs translation of the OVA, characters 'Tetori', 'Ziggitalis' as well as the Gunmen 'Zaolegg' and 'Usappyon' were referred to as ‘Chitori’, 'Jigitalis', 'Daorek' and 'Usaggon’ respectively. They have been updated here to correspond with the remastered subs for the episode released with the fan translation patch of the NDS game, which used more accurate approximations based on abbreviations found in the game files.
 * 'Usapyon' doubles as a slang for "Just kidding!" as well as a combination of the words usagi (rabbit) and pyon (onomatopoeia for a hopping noise), hence why Kamina names the Gunman "Usappyon" after seeing its rabbit-like appearance.