Well, there are quite a few episodes, but time wise for me the shortest anime ive seen is Hetalia: Axis Powers/ world series. Anyone else seen it knows, there only 5 minute long episodes, and should be flipping longer... and the opening should be shorter. neutral
12/13 series ( or half seasons ) are pretty common they aren't exactly "short" but, they aren't "average" I would say anything under 12 episodes would be short
The Heroic Legend of Arislan - Age of Heroes has 6 episodes.
Super Mobile Legend Dinagiga - 2 episodes.
Princess Rouge: The Legend of the Last Labyrinth - 2 episodes.
Legend of Lemnear - 1 episode.
Xanadu Dragonslayer Densetsu - 1 episode.
Redline - 1 episode.
Kaidohmaru - 1 episode.
Karas - 6 episodes.heart
Robot Carnival - 6 episodes.
Virtually Real - Cybervenus FeiFei - 6 episodes.
Cleopatra D.C. - 3 episodes.
World Reflected in the Pupils of a Girl Watching the Sky - 9 episodes.3nodding