Likable characters, episodic comedy and a setting which allows heading off the new years celebrations and then going home, shrinking down, arming up, and fighting the aliens infesting your teeth.
There's some references, but they aren't thick and fast, and they don't do much lolrandom humor.
Also very accessible thanks to the wonderful narrator who finally got his rightful spot in the OP in season 5.
Basic episode plot: It's a normal day at the Hinata residence when Keroro does something stupid in another failed attempt to take over the world. They spend the rest of the day getting distracted, having fun, and cleaning up the mess.