People often associate yawning and positioning one's arms behind the head with getting ready to kick back after a long day. The pose is associated with relaxation, and isn't typically meant for public spaces. However, this pose is prominent in shonen anime -- primarily with male characters who walk around with their arms behind their heads. They sometimes even yawn and keep their eyes closed. Shonen anime boys who walk around like this are typically characterized as easygoing, and perpetually sarcastic.

Of course, these same characters also possess enough power to wipe out droves of people with minimal effort. This pose is usually associated with characters who are brilliant, but love to slack off, or else refuse to apply themselves, because they hate giving their all. Naruto's Shikamaru is a great example of this trope, as is Assassination Classroom's Karma Akabane. Hunter x Hunter's Killua Zoldyck is...