The Neo Armstrong Cyclone Jet Armstrong Cannon (Japanese: ネオアームストロングサイクロンジェットアームストロング砲) is a legendary and powerful weapon used by the Inuisei Amanto when they first arrived on Earth and it gave them an overwhelming advantage over the Earthlings, assuring their takeover of Edo and Earth. This weapon was also used in several other galactic wars throughout history. Oddly enough this mighty weapon looks somewhat
like sausage and manberries familiar.
It made its first appearance in Episode 38, as Gintoki and Kagura's snow sculpture that was recognized by several characters (with different origins provided by them, including Gintoki), except for Shinpachi who simply thought it was
a penis an obscene sculpture. The sculpture was later upgraded with a pair of wings & a slide based on some parts from Hasegawa & Katsura's sculptures. During the snowball fight, the sculptures are separated and used as weapons by Gintoki & Kagura.
It made another appearance, later on in Episode 57, fused with a Justaway to form the ultimate weapon, the Justtank, powered by Soopah-Powah Batteries, the greatest source of energy in the galaxy. However, ultimately, it was just porn (admitted by Gintoki and Kagura).
In Episode 237, it makes a short appearance when Kagura was building one out of snow, just like the original but the size was much larger. The parts were then used when Okita and Kagura started fighting.
Gengai made a larger version of the cannon, named Neo Armstrong Cyclone Jet Armstrong Gengai, in Episode 346 to fight the Altana Liberation Army. He said that he has been working on the giant machine since the Joui Wars.
Shinpachi also famously screamed "THE EARTH GREW A PENIS!"
- Armstrong Guns (which somewhat contributed to the naming of this cannon) were in fact real world cannons, designed by Sir William Armstrong and were instrumental in Japan's opening up. Several of those cannons (with their base) do vaguely resemble the cannon in Gintama.