Monster Factory (怪獣工場 Kaijū Kōjō) is the thirteenth episode of Ultraman Dyna.
Three young boys are searching the grounds next a river in hopes of uncovering the "UFO parts" spotted by one of them, Takeshi. However once they discover the fragment, they find that it is marked with the "Made In Japan" label. The other two boys ditch Takeshi due to his lies, which prompts him to throw firecrackers at them.
Once Takeshi had returned home, he is scolded by his mother for his violent outburst prior. By sheer chance, Takeshi spots from his bedroom window a glowing object falling to the ground. He thinks this to be a UFO and runs to the scene. There he finds three strange men and a large box of goods. Though, he soon discovers that the three men were actually aliens; and manages to spot a mechanical kaiju being assembled. Takeshi calls the police and Super GUTS - of which officers Kariya and Asuka arrive.
The two officers attempt to storm the factory that Takeshi had claimed was the grounds of the aliens, but they are greeted with a completely normal factory with three workers earnestly working hard at creating toy kaiju. No such suspicions of aliens seemed to be true; so as such, Takeshi was returned home. While Kariya learns from the boy's mother that he often tells lies to garner attention, Asuka indulges himself on Takeshi's comedy manga - of which he finds greatly amusing. He even took some back with him with a promise to return them to Takeshi the next day.
That night, Takeshi snuck out of his house on his own in an attempt to prove his case. He managed to infiltrate the factory but is forced to hide once the Alien Mijir return. He is eventually spotted but manages to escape and outrun them using his trusty firecrackers. Back at the Super GUTS headquarters, Asuka has trouble containing his laughter as he continues to read the manga he borrowed from Takeshi. Captain Hibiki finds him and brutally scolds him; though he is saved by a call from Takeshi claiming to have seen aliens. Asuka is reluctant to depart, but is forced to once Takeshi blackmails him with reporting Asuka for stealing his manga.
Asuka and Takeshi enter the factory and are taken by surprise and subsequently captured by the Alien Mijir. Mijir Doruchenko explains his plan to colonize Earth using the 400m tall Garaon. As the sun begins to rise signalling the dawn of a new day, the Alien Mijir are distracted, Using this opportunity, Asuka and Takeshi fight back and escape the factory. In the ensuing chaos the Mijir are forced to mobilize their incomplete Garaon.
Super GUTS attempt to intercept the beast but are led in circles thanks to Garaon's multiple faces and fighting styles confusing them. Asuka transforms into Ultraman Dyna (character) and does battle with the machine - inhaling a great portion of laughing gas in the process. To combat the tri-faced threat, Dyna dons Miracle Type and multiplies himself to attack simultaneously from three angles. His continuous strikes and Hand Shooter force the Mijir to flee. Afterwards, Takeshi is returned home and reunited with his friends.
- Shin Asuka (アスカ・シン Asuka Shin): Takeshi Tsuruno (つるの 剛士 Tsuruno Takeshi)
- Gousuke Hibiki (ヒビキ・ゴウスケ Hibiki Gōsuke): Ryo Kinomoto (木之元 亮 Kinomoto Ryō)
- Toshiyuki Kohda (コウダ・トシユキ Kōda Toshiyuki): Toshikazu Fukawa (布川 敏和 Fukawa Toshikazu)
- Ryo Yumimura (ユミムラ・リョウ Yumimura Ryō): Risa Saito (斉藤 りさ Saitō Risa)
- Kouhei Kariya (カリヤ・コウヘイ Kariya Kōhei): Takao Kase (加瀬 尊朗 Kase Takao)
- Tsutomu Nakajima (ナカジマ・ツトム Nakajima Tsutomu): Joe Onodera (小野寺 丈 Onodera Jō)
- Mai Midorikawa (ミドリカワ・マイ Midorikawa Mai): Mariya Yamada (山田 まりや Yamada Mariya)
- Mijir Doruchenko （ミジー・ドルチェンコ Mijī Doruchenko): Kinzou Sakura (桜金造 Sakura Kinzō)
- Mijir Udochenko (ミジー・ウドチェンコ Mijī Udochenko): Shinichi Satou (佐藤信一 Satō Shinichi)
- Mijir Kamachenko （ミジー・カマチェンコ Mijī Kamachenko): Osamu Nakajima (中島修 Nakajima Osamu)
- Ultraman Dyna
- Flash Type
- Miracle Type
- Ultraman Dyna Volume 4 features episodes 13-16.