Lt. Col. Glenn Manning is the central character of the movies The Amazing Colossal Man and War of the Colossal Beast, featured in Season 3 of Mystery Science Theater 3000. Manning, participating in a nuclear test at the beginning of the first movie, is irradiated and grows to the height of 60 feet.
In The Amazing Colossal Man, Manning is portrayed by Glenn Langan (credited as Glen Langan), who appeared as Captain Ross in Women of the Prehistoric Planet, and also had a recurring role as Victor Tribolet in the TV series Hondo.
In War of the Colossal Beast, Manning (who is disfigured and unable to speak) is portrayed by Duncan "Dean" Parkin.
In both MST3k episode segments, Michael J. Nelson cameos as Glenn, ostensibly taller than 60 feet as he's able to reach the Satellite of Love.