Doc shows Marty McFly (out of frame) the newspaper with the EMMETT BROWN COMMITTED front page news story.

Mental Ward B was a mental ward in the Hill Valley Hospital.

On May 23, 1983 in the Biffhorrific timeline, Dr. Emmett Brown was declared legally insane and was sent to the mental ward at the hospital.

This was reported on the front page of the Hill Valley Telegraph under the headline EMMETT BROWN COMMITTED - Crackpot Inventor Declared Legally Insane, which was accompanied by a photograph of Doc outside the ward, restrained by orderlies, wearing a straitjacket.

After Marty McFly burned Grays Sports Almanac in 1955, the timeline was restored to normal and the aforementioned newspaper headline changed to report the true events of May 23, 1983, EMMETT BROWN COMMENDED - Local Inventor Receives College Grant.