Glenn was an astronaut for the World Space Authority flying to the recently discovered Planet X with his colleague Astronaut Fuji. When the two arrived on Planet X, they were taken into an underground Xilien compound and were made to wait until they were introduced to the Controller of Planet X. The Controller informed the astronauts the reason his people could not live on the surface was because of a horrible space monster called "Monster Zero," which Glenn immediately recognized as King Ghidorah. The Controller asked if the humans would give them Godzilla and Rodan to combat Ghidorah in exchange for a cure for cancer. Glenn and Fuji returned to earth, and told the World Space Authority of the Xiliens' offer. While on Earth, Glenn continued a romantic relationship with a woman known as Miss Namikawa. Glenn informed Fuji that one night he and Namikawa were staying at a small lakeside house, and he swore he saw the Controller in their room during the night, causing Glenn to become suspicious of the Xiliens. Glenn and Fuji then traveled to Lake Myojin, where the Xiliens claimed Godzilla was sleeping. There, they witnessed three Xilien UFOs emerge from the lake, despite the Xiliens' claims that they had no presence on Earth. The Controller emerged from a UFO and apologized for showing up unannounced, but revealed that Godzilla and Rodan were in fact in the locations he had earlier claimed they were. The Xiliens' UFOs proceeded to capture Godzilla and Rodan and prepared to transport them to Planet X. It was decided that Glenn, Fuji, and their superior, Dr. Sakurai of the World Space Authority should be taken to Planet X to oversee the operation to repel Ghidorah and obtain the formula for the promised medicine. While on Planet X, Glenn discovered two Xiliens women who look exactly like Miss Namikawa. After Godzilla and Rodan fought and drove off King Ghidorah, the three humans were transported back to Earth in a replica of their original spacecraft. When the Xilien tape supposedly containing the cancer cure was played, it was revealed to be the Xiliens' declaration of dominance over earth. Glenn then found Namikawa wearing an Xilien uniform, and revealed that he knew what she was. Namikawa apologized for misleading Glenn but revealed that she truly loved him and wanted to marry him and live with him on Planet X. Glenn told Namikawa that he would never submit to the Xiliens despite Namikawa's protests, when a group of Xiliens entered the room to arrest Glenn. Glenn kissed Namikawa before the Xiliens could take him away, only for Namikawa to be immediately executed by the Xiliens. Enraged, Glenn asked the Xiliens' Earth commander why they killed Namikawa, to which he replied that she violated the computer's demands. Glenn was then brought to a prison cell below the lake house that was the Xilien earth base. Glenn discovered a note left in the cell by Namikawa, which revealed that the Xiliens were helpless against a certain sound. Glenn's cellmate Tetsuo Teri realized that the sound was his Lady Guard alarm, which the Xiliens had posed as a toy company in order to purchase from him. Tetsuo used the alarm to immobilize the Xilien guards, and he and Glenn managed to escape the Xiliens' base. Glenn and Tetsuo delivered the alarm to the World Space Authority, who formulated a plan to mass-broadcast the sound and render the Xiliens helpless. The sound was broadcast over radios around the world, and the helpless Xiliens were then eliminated by the military. After the subsequent battle between Godzilla, Rodan, and King Ghidorah, Dr. Sakurai informed Glenn that he and Fuji would act as ambassadors to Planet X in order to perform peace negotiations.
- Glenn is most likely named after the real-life American astronaut John Glenn.
- Glenn was one of two roles for American actor Nick Adams in a Toho kaiju film. Adams also portrayed Dr. Bowen in Frankenstein vs. Baragon, released the same year as Invasion of Astro-Monster.