Ex Ray is an orange monster who appeared in the Scrubs episode "My ABC's", along with other characters from Sesame Street. The new monster is a patient of Sacred Heart Hospital in one of J.D.'s fantasies.
In the fantasy sequence, J.D. gives Ex Ray some bad news, explaining that the monster has a hand inside it. "That explains so many things," the monster sighs.
He appeared again, this time on Sesame Street itself in a season 40 episode (performed by Jim Martin). He's seen inside Hooper's Store alongside the Count and Sherlock Hemlock. It was an on-topic appearance, as the storyline dealt with x-rays.