The sequences with Ultraman fighting proved to be so expensive to film, that the producers needed a way to limit the scenes to only a few minutes for each episode. The solution was to give the character the weakness that he can not survive in his true self for more than roughly three minutes before he runs out of energy. This is marked with his warning chest light, called the Colortimer, which begins to blink with increasing speed as his energy runs out.
As is the case with his previous series, Urutora Q (1965), series creator Eiji Tsuburaya uses and redecorates famous Toho monsters for the show. Baragon (from Frankenstein Conquers the World (1965)), who was also used in aforementioned series (as the monster Pagos), was used as monsters Neronga in Episode 3 ("Sally Forth, Science Patrol!") and Gabora in Episode 9 ("Operation Lightining Speed"). And the King of the Monsters himself, Godzilla (who was also used as the monster Gomess in the first episode of Q), was used as the frillnecked lizard monster Jirass in Episode 10 ("The Mysterious Dinosaur Base"). Using the body of the "Mosu-Goji" suit and the head of the "Daisensô-Goji" suit, Godzilla/Jirass was fitted with a frill collar around his neck, as well as a minor paint job. This was because the script called for a lizard monster, so Eiji said, "Okay, then, let's use a Godzilla suit!"
Some monsters from Urutora Q (1965) appear in this series, some with changes. A few examples: In Episode 4 ("5 Seconds Before the Explosion!"), Ragon, the Gill-Man-style humanoid fish, returns in giant size and breathes fire like Godzilla. In Episode 8 ("The Lawless Monster Zone"), the monster Pegila returns as the monster Chandrah, fighting the monster Red King (and loses). And in that same episode, the giant-sized robot monster Garamon is reused as the friendly, pint-sized monster Pigmon.
The character of Ultraman went through many changes as pre-production went along. At first, the planned series "Woo" had a corporeal space creature with eyes, who befriended a reporter named Jôji Akita, but the Self Defense Forces were after him. This was basically the monster version of Doctor Who (1963), and Woo's personality was comical. Then they planned "Bemular" (retitled "Science Patrol - Bemular") about a defense force disguised as an art/photography team. One of the members, little did anyone know, gained the ability to transform into a giant birdlike humanoid monster called Bemular (this is not the same Bemular that Ultraman would fight in Episode 1), who defends Earth from monsters, aliens and other threats. Unlike Woo, Bemular was a tough and righteous fighter (Bemular looked very similar in design to the title monster of Daikyojû Gappa (1967)). This then evolved into "Redman," the title hero of which slightly resembled Ultraman as we know him, but he looked more demonic and had horns. Both Bemular and Redman were designed by Tôru Narita, who came up with the final design for Ultraman based on his Redman design, now resembling a less-scary Buck Rogers-style alien being (with a bit of the iconic "Roswell Alien" as well). The characteristic "ColorTimer" (the "warning light" on his chest) was added at the eleventh hour.
When directing Episode 36, "Gift from the Sky", Akio Jissôji played a humorous prank on star Susumu Kurobe by making him mistake a spoon for the Beta Capsule when transforming into Ultraman. This became a popular in-joke to many fans of the show (even American fans like cartoonist Jeff Nicholson, who made an Ultraman parody called "Ultra Klutz", in which the title superhero transforms using a spoon).
For about the first third of the series, the opening credits featured silhouettes of monsters that had appeared in "Ultra Q", such as Kanegon and Gorou. For the remaining episodes, silhouettes of "Ultraman" monsters like Gyango and the iconic Baltan were shown instead.
The sound of the telephone ringing at Space Patrol headquarters is also one of the sounds used for the monster King Ghidorah from such Godzilla movies as Invasion of Astro-Monster (1965) and Destroy All Monsters (1968). (Much like the re-use of monster suits and sets, the use of this sound effect is not a direct reference to these films.)