Lou Holtz was a muppet, literally. The actual Lou Holtz died in 1989 and was replaced by a creation from the Jim Henson studio. The plush, orange, googly-eyed muppet filled the coach's former role: bouncing up and down the ND sideline, flailing his arms a bit, and occasionally explaining the difference between near and far. He would later do the same at South Carolina.
If you look closely at old game films, when an opposing team's back is streaking down the field, past the ND bench, you can occasionally see the rods they used to move Muppet Lou's arms, or one of the black-clad puppet wranglers positioning his arm up Lou's a$$ (as part of their exclusive television deal, NBC never showed close-ups of the muppet, and would seamlessly add older footage of the coach when one was needed).
After his "retirement" (one of his eyes fell off during an S.C. - Kentucky game, luckily no one was watching) ESPN bought the rights to Muppet Lou, and in conjunction with Industrial Light and Magic created an eerie, alomst human looking CGI Holtz model, Lou 2.0. The creation is voiced by veteran character actor Hank Azaria, who while a talented perfomer will be the first to admit doesn't know sh#t about football.