U.S. actor Danny Glover is to guest star in an episode of the new drama series \"Ironside,\" NBC announced Friday. The \"Lethal Weapon\" and \"The Color Purple\" star will play the title character\'s father Frank in a flashback sequence. The episode \"reveals some insight into Ironside\'s family history in the last days before his father enters prison,\" the network said in a news release. Blair Underwood plays Robert Ironside, a brilliant, wheelchair-bound police detective, in the show, which is to premiere Oct. 2.