Dean knew that even though their mom had been around Sam for a while she probably hadn't got up to speed on Sam's different looks when they were hunting. This was one that was very familiar to him so he picked up his pace to get closer to Mary. Plus it was an added bonus that he could see for himself how she was since he was an old hand at fighting through his own pain.

"That lifted brow, if you can see if through Sam's shaggy hair..." Dean smirked because he would never let a chance to jerk Sam's chain about his hair go by. "means let's let the thing go so we can follow it back to its lair, den or whatever place it came out of. Sound good?"