Some of the footage from the original Godzilla (1954) was recreated with the new Godzilla suit, since Godzilla's appearance has changed so much from the original version.
Although they do not look alike, the Meganuron (a.k.a Meganulon) in this movie is based on the Meganurons that attack the villagers in the Toho monster movie classic, Rodan (1956).
Toho continued their tradition of casting actors from their science fiction films of the 1950s and 1960s. The character of Yoshino Yoshizawa is played by Yuriko Hoshi who had previously starred as Yoka in Mothra contre Godzilla (1964) and as Naoko (a completely different character) in the sequel Ghidrah, le monstre à trois têtes (1964).
Both Megaguirus' name and design were inspired by the real life Meganeura insect that lived during the Carboniferous period, around 300 million years ago. Though commonly called a giant dragonfly, Meganeura actually belonged to the griffinflies, a group of enormous flying insects that went extinct 250 million years ago. The real Meganeura's wingspan was only 70 cm or just over two feet, though it was possibly the largest flying creature of its time.
The infamous "Giant Leap" Godzilla performs against Megaguirus during the final battle is a tribute to Godzilla suit actor Tsutomu Kitagawa's stuntwork in Toei's Super Sentai Series (featured as Dynaman (1988) and "Power Rangers" in the US).
Masaaki Tezuka: is seen in a white shirt during a post ending credits sequence on a playground with school children. Post Ending Credits cameos are a kind of trademark of Tezuka's, as he in one in every Godzilla film he's directed.