Blair Brown joins a growing cast that also includes new recruit Mary Steenburgen
Actor has chosen to leave the role for a lead part in a new HBO comedy co-starring Jack Black and Tim Robbins
"The fact that recognize me for that character is a very positive thing," he said on Thursday night's "Jimmy Kimmel Live"
"Lethal Weapon" star Glover will play Ironside's father in a flashback sequence
The teaser for the HBO Film's movie shows a mix of new acting and archived footage