Sgt. Frog (Keroro Gunsou), to put it loosely, is a show about alien frogs trying to take over the earth. The mission to invade Pekopon (earth) is abandoned due to the fact that human beings love dissection and the four five member crew is left on their own. The Keroro Platoon has no knowledge of this, but it doesn't matter as the mission is scrapped in favor of the rich ammenities of earth, namely Gundam models.
The inclusion of Gundam, let alone anything mecha related, will often times alienate entire audiences as they hate the particular genre. Those that absolute adore everything that is mecha will ultimately love the show. For everyone else, there is something in it for you to fall in love with as well. Follow the jump for my recommendation for Sgt. Frog.
Sgt. Frog
Creator: Sunrise Animation
Publisher: FUNimation
Release Date: September 22, 2009
MSRP: $49.99
Sgt. Frog has something for everyone. Making its anime debut in 2004 and being serialized in manga since 1999, Sgt. Frog has largely succeeded due to its comedy based on word puns and referencing the hell out of everything from the past 20 to 30 years. It's no surprise then that a couple years later, we see the explosion of shows emulating the same formula (Hayate, Lucky Star, etc.) It's not a concept developed by Keroro, but they made it successful.
The manga and character designs are done by Mine Yoshizaki. If the designs look familiar, it's because he designed the characters for Konami shooter Otomedius, Soul Calibur IV's Angol Fear (who is related to Sgt. Frog's own destroyer of worlds Angol Mois), and various other doujinshi and figures.

(From left to right: Tamama, Dororo, Kururu, Giroro, and Keroro)
Why should you watch Sgt. Frog though? Honestly, I love the series to death and it has nothing to do with my devotion to the cult of Gundam. It's a show where you can jump in and just enjoy. The plot is simple and is just a great diversion for the day. The characters are enjoyable and there is nothing that could make you hate any of them. The cast will only make you want to buy toys of all of them. Being that Bandai owns 49% of Sunrise, they won't be hard to find.

(Above is a reason why you'll love this show: Aki Hinata. She's a loving mother. She's beyond hot. She's a manga writer, confessed geek, and rides a motorcycle. Is there anything else you want in a woman?)
Going back to the DVD, I want to personally thank Funimation for saving this series. When ADV had originally purchased the rights in 2007, characters were renamed and mentions to the Gundam franchise were removed. I cringed at what was previewed. Thanks to fan suggestions and Funimation's reasoning to actually listen to them, the show is left intact as it was meant to be. There are references for everything from Galaxy Express, Space Battleship Yamato, Kamen Rider Den-O, and Keroro dressing up as Char Aznable in the classic bar scene. Also, Natsumi kicks ass, namely Keroro and Giroro's. If you followed the fansubs, you won't be disappointed with the treatment given to it by Funimation. While the dub does take liberties, such as Natsumi swooning over Christian Bale as Batman, the subtitles are left in tact to the original Japanese.

When you crack open the disc, you'll get the standard extras, namely textless opening and ending. The ending theme, Afro Gunsou (Sergeant), is perhaps the greatest ending of all time. It's 3D rendering of Keroro in a tassled jacket, afro, and dancing disco. How do I know it's the greatest, best thing ever? There's a model kit of it.
You can get your hands on the first 13 episode set right now at your usual anime stops for the MSRP of $49.99, but you can always get a better deal if you look around. The second volume, consisting of episodes 14 through 26, will be released on November 22nd for the same MSRP of $49.99.
I also need to continue the manga (at volume 7 currently).