Multiple Personality Disorder: An extremely rare mental disorder where a person's mind is split into two or more personalities that attention-desperate teenagers pretend to have so people will think they're unique/cool/troubled/not a loser, etc.
Andy doesn't have MPD, he's just an attention whore.
Multi personality disorder, or DID dissociative identity disorder, is a mental illness in which the person has 2 or more personalities inside one mind. It is often caused when a child is repeatedly sexually, mentally, or physically abused and cannot physically escape the situation.
1) Dan's daughter was raped so many times when she was very little, she has MPD to cover up the pain.
2) Jeff beat his son so much, he made up more personalities so he could forget the pain.