Mambu

Mambu (マンブー), known as Flying Shell in some English sources, is a reconnaissance robot that can only be harmed when it opens its shell, exposing its eyes. Upon opening its shell, it releases shots that spread out in eight directions.

Mega Man
Mambu appears in Bomb Man's stage and Cut Man's stage in the first Mega Man game. When one Mambu is destroyed or leaves the screen, another Mambu will appear, spawning endlessly, one at a time. In Bomb Man's stage, it is possible to stop their appearance by freezing one with Ice Slasher and taking distance to make it disappear from the screen.

Bug
The original NES game has a bug where if a Mambu is scrolled off the screen while its shell is still open, the next Mambu will fly in with its shell open rather than closed. The bug will fix itself when the Mambu has fired its shots.

Other Media
Flying Shells appear in Captain N: The Game Master.

Etymology
Its name is possibly a combination of the words, "manmaru (まんまる)" and "boule". The former is Japanese for perfectly round. The latter is French for ball, pronounced as "būru (ブール)" in Japan.

Similar Enemies
Enemies similar to Mambus.
 * Met
 * Pukapelly
 * Diarn