Shenron is shown with the horns of a stag, sharp teeth, green scaly skin, red eyes, four toes on each foot, a long serpentine body (his tail takes up three-fourths of his length), long flowing whiskers, a long snout, crescent shaped nostrils, and flowing green hair on his cheeks. He is an Eastern dragon, whose kind are benevolent and sacred in Oriental mythologies. Unlike the Western dragons, which have large dorsal foldable wings on their backs, he has none. His kind are good at heart, but as a strong dragon, he has an aggressive temper, and is impatient sometimes (for some reason more so than Porunga, the Namekian Dragon).
Shenron as he appears in Dragon Ball   Shenron can be summoned by gathering all seven of the Dragon Balls of Earth. Shenron can bestow any wish as long as it does not exceed the power of his creator, who must be still alive (i.e. Kami/Piccolo or Dende). Shenron has also threatened to kill the summoner if they do not say a wish on time, or if they do not say a wish at all (although he has only actually attempted to kill someone in the "Tree of Might," where Gohan's friend dragon Icarus tries to attack Shenron). According to Goku, Shenron cannot (or will not) grant the same wish more than once. The Dragon Balls cannot be used for one year after a wish is made, as they turn to stone. The Earth Dragon Balls are relatively small, each about the size of a large orange. The Shenron of the Black Star Dragon Balls is red, opposed to the Shenron of Earth who is green. Unlike Porunga, Shenron can only grant one wish per summoning, until Dende upgrades him to grant 2 wishes.
Shenron can wish back more than one person per wish, provided that they died less than a year ago, died under a common circumstance (e.g. killed by a certain villain), and have not already been wished back before. This is used to revive the victims of many villains, such as King Piccolo and his men, Frieza and his men, and Cell.
Shenron in the manga   In the King Piccolo Saga, after King Piccolo uses the Dragon Balls to regain his youth, he murders Shenron before he can disperse to prevent anyone else from using the Dragon Balls against him. However, after his defeat, Kami revives Shenron to reward Goku for his valiant efforts against King Piccolo. He had originally decided not to recreate them, as he originally designed the balls to encourage acts of bravery and give people a sense of hope, but the selfishness and greed of mankind caused the Dragon Balls to be used in the exact opposite manner than that intended. It was only upon Goku displaying his undying love for his friends that he decided that there were, indeed, good people left in this world. Shenron was later used to revive Goku in order to defend the planet from the Saiyans. Shortly thereafter, Shenron was indirectly killed by Nappa after Piccolo was killed taking an attack meant for Gohan (since due to his creator Kami's connection to Piccolo, Kami ended up dying the same time as Piccolo). He was indirectly revived by the Namekian Dragon Balls after Gohan and Krillin wished for Piccolo to be revived and transported to Namek. Shenron was later used to wish everyone who was killed by Frieza and his Empire, although it barely worked because Shenron himself was unsure whether the wish could be fulfilled. Shenron was later temporarily killed after, due to extreme circumstances during this time, Kami decided to rejoin with Piccolo, and Piccolo likewise agreed.
Shenron listening to Lord Slug's wish  After Dende's remodeling, if a person only needed one wish, then the Dragon Balls would scatter around the world in the same way as if someone had spoken both wishes. However, the Dragon Balls will only become stone for four months, allowing the finding of the Balls and summoning of the Dragon eight months faster than usual. Using the Dragon Balls this way allows only one wish the next time Shenron is summoned. Afterward, the balls scatter and turn into stones for a whole year, the next time allowing the two wishes it normally grants. Also, in the manga, It was implied during the Buu Saga that Dende may have upgraded Shenron during the seven years of peace, as Goku mentions that they have two wishes left after they wished for all the people killed that day back to life, but Piccolo replies that the immense amount of revivals during that time had consumed most of the Dragon Balls power to the extent that it could only allow one more wish.
Shenron in Dragon Ball GT   In Dragon Ball GT, an evil dragon, known as Black Smoke Shenron in the English dub, is invocated from the cracked Dragon Balls (which were cracked because of Negative Energy), which emits seven individual dragons. Goku, along with his family and friends, are significantly inconvenienced and must battle them resulting in the Shadow Dragon Saga. After Goku and the other Z Warriors defeat the Shadow Dragons, Shenron appears without being summoned. He heals Goku's wounds and grants one last wish before he leaves the Earth with Goku and the Dragon Balls in order to recuperate and teach the Earth's inhabitants to stop relying on the Dragon Balls to solve their own problems. One hundred years later, Shenron presumably returns, as the Four-Star Dragon Ball is seen again.