It's normal. They do have rather large little manhoods though! My chihuahua is well endowed for such a tiny dog.
If it ever gets stuck, use a water based lubricant (yes, the kind for people) to moisten it and get it back where it belongs. If it's swollen at the base (called a knot), that must go down before it can return to the sheath. If it does not go down, a cool damp cloth will help pull the blood back into the body. |