During Frank Castle's hearing, a supposed x-ray of Frank's skull was being projected into the screen while the doctor was being cross-examined. The x-ray image only shows the skull but without the mandible (jaw) like you would normally see in skull x-rays, thus making the x-ray of Frank Castle's head wound resemble Marvel's classic Punisher skull logo that wears on his t-shirts in the comics.
Clancy Brown, who plays Colonel Ray Schoonover in this episode, has lent his voice to other Marvel franchises including Thor: Ragnarok (2017) as the voice of Surtur, The Avengers: Earth's Mightiest Heroes (2010) as the voice of Odin, Ultimate Spider-Man (2012), Hulk and the Agents of S.M.A.S.H. (2013), as well as DC Comics' The Flash (2014) and was the voice of Lex Luthor for Justice League (2001).