Michael "Big Mike" Heck Sr. is the father of Mike and Rusty Heck and the grandfather of Axl, Sue and Brick Heck. He is a widower and a hoarder, and recluse, who very rarely leaves his house. He can be very stubborn at times, as proven in Thanksgiving and Thanksgiving II when Mike had to beg him to come over to the Heck's House. Big Mike is often quoted saying "I don't want to be a bother," a trait he seemingly passed down to Rusty.
He is portrayed by John Cullum