Dr. Iplier (pronounced "E-plier") is one of Markiplier's alter egos. The Doctor has many mental problems and is known for yelling at nurses to "shut up!"
Dr. Iplier seems to always be wearing a head mirror and lab coat.
Dr. Iplier informs a patient, Ryan, of a number of things he shouldn't know, such as his parents kicking him out and that his dog was run over. When Ryan tries to leave the doctor tells him his girlfriend is cheating on him with fellow Cyndago member, Daniel. A bit later he adds that Ryan's parents are dead. To console him Dr. Iplier tells him he dosen't have diabetes, then proceeds to laugh at a video of his parents car crash.
In Wilford Warfstache's project, "Markiplier TV", Dr. Iplier plays himself and informs multiple people that they're dying. Afterwards when Wilford asks a table of egos their opinion on it, the doctor says that it's okay, adding that it painted him in a good light.