Super Deformed Gundam or SD Gundam originated from a contributed illustration of a junior high school student from Nagoya by the name of Koji Yokoi to the "Model News" magazine that Bandai was issuing in the 1980s. The illustration is of a Gundam but with the weird proportion where the overall height of the Gundam is equal to 2 of its heads. This illustration interested the chief editor and so leading to Koji Yokoi serializing SD Gundam in 4 frame comics in "Model News".

​

Reference: https://gundam.fandom.com/wiki/SD_Gundam