Source: Pwtorch.com

The Undertaker appeared on Monday's RAW SuperShow and did not remove the hood covering his head. WWE officials plan to have the iconic wrestler remove his hood and display his altered appearance for the first time when he faces Triple H in a Hell in a Cell Match at WrestleMania XXVIII. Though he shaved his head bald last year, the Pro Wrestling Torch reports he has maintained the look since then and therefore will not appear similar to his "Big Evil" persona of 2002 and 2003 when he had short hair.

As far as why The Undertaker went through the radical change, it is said that he considered the hair a nuisance to deal with on a daily basis.