Sleepy Dragons were once domesticated as pets, easily tamed due to their patient demeanor and lazy dispositions.
Sleepy Dragons have typical dragon features including hard scales, wicked looking horns and sharp claws, but these dragons rarely feel compelled to use these attributes for battle or hunting. They much prefer sleeping, and remain inactive for most of the days, not unlike a house cat. They enjoy cozy environments and much prefer a warm fireplace to a wet, cold and expansive cavern.
Sleepy Dragons were once a staple in any respectable castle. They were usually docile and gentle, and could often be found curled in a corner, but the presence of one of these dragons sent a message to anyone who would seek to harm the residents of a dwelling. They were fiercely protective of those who gave them shelter, and would be quick to defend their homes if faced with a threat.
These dragons were considered tame and domesticated, but it is likely the dragon was an active participant with its own interests in mind. Allowing humans to believe it was their "pet" was a small price to pay in return for the guarantee of a safe place to curl up and rest.
These dragons are not as plentiful as they used to be, as castles are not the most common structures anymore and Sleepies find modern houses a bit too cozy in most cases. If they are to be encountered, it will likely be in the ruins of an ancient castle, sleeping the day away and reminiscing of cozier times.