Sgt. Frog

Sgt. Frog  (ケロロ軍曹, Keroro Gunsō, lit. "Sergeant Keroro": internationalised as Sgt. Frog by Funimation) is a manga series that began serialization in 1999 by Kadokawa Shoten 's Shōnen Ace, and received its own anime adaptation in 2004. Sgt. Frog references can be seen in both the original Lucky Star manga and its subsequent anime adaptation, due to the Comptiq magazine that Lucky Star was first serialized in, also being a property of Kadokawa Shoten.

The following references are seen in the Lucky Star anime:
 * Sgt. Frog toys can be seen inside a claw crane machine in episode 2.
 * In episode 7, a Keroro keychain can be seen on Tsukasa's phone. It ends up on Tsukasa's bag after she loses her phone. Later on, both Konata and Tsukasa say that their favorite manga is Sgt. Frog.
 * In episode 10, Tsukasa's new phone comes with a Tamama keychain.
 * In episode 12, a cosplayer dresses up as Keroro. Later on, a Keroro poster is seen on the wall where Meito Anizawa and Tomokazu Sugita are punched towards by President Takahashi after he sees them argue over their characters.
 * In episode 13, one of Meito's assistants is a blonde-haired woman whose apron has a yellow star print similar to the one on Keroro's chest. Another of Meito's assistants is of a shorter stature and wears a bob tail, similar to Tamama. A third assistant, a male wearing crimson-red clothes, is a reference to Giroro. The preview for episode 14 is voiced by Keroro, Giroro and Tamama.
 * In the OVA, Minoru Shiraishi, as a pet shop owner, offers Konata, Kagami, Tsukasa and Miyuki two frogs that look like Keroro and Tamama. Their croaking hypnotizes the girls and turns them into frogs.