In years past, you'd always see them outside convenience stores and in parking lots, coping a squat next to their Subarus and Hondas, smoking cigarettes. They were tough looking. They were thugs. And they'd sit like they're squeezing out turds.
In Japan, there's a style of squatting called "yanki zuwari" (ヤンキー座り) or "Yankee sitting". Here, the Japanese word "yanki" (ヤンキー) does not refer to Americans or "Yankees". Rather, it refers to the slang for a type of juvenile delinquent that appeared in the 1970s and 1980s.
That style of sitting enabled them to cop a squat anywhere and rest their elbows on their knees while puffing on cigarettes. Yanki talked and acted lower class, and this trademark manner of sitting wasn't exactly polite. This squatter's ass barely hovered above the ground, and their crotch was wide open—a far more blunt version of the standard squat. Yanki zuwari made people look like they were going number two, hence the other name for that style of sitting: "unko zuwari" (うんこ座り) or literally "poop sitting", because it mimics the squatting style used with traditional Japanese toilets.
Yanki zuwari often appears in manga, TV, and video games. Whenever juvenile delinquents are shown in Japanese pop culture, they are often squatting like they're taking a dump. For example, during the last Kamen Rider series, Kamen Rider Fourze, the hero was a delinquent student, and the show featured inevitable yanki zuwari. It's trope. It's trite.
Not only that, but the style of sitting is parodied. Recently, at a toy fair in Tokyo, a figure of Ultraman kaiju Zetton doing yanki zuwari was on display. Photos, like this one from Japanese website Moeyo.com (NSFW), soon went viral, appearing on Japan's largest bulletin board 2ch, with people commenting how funny it was to see this monster squat like a delinquent. Likewise, the 3D art image (link NSFW) at the top of this article is rife with yanki zuwari parody.
While yanki zuwari lives on, yanki saw their heyday in the 1980s and 1990s. Today their numbers have decreased, but they still exist: Earlier this year, an online dating service aimed at yanki launched in Japan.