Galvantula is a yellow arachnid Pokémon. Its body consists of a head and abdomen. Its head is yellow on top and light purple on the bottom. It has two large, blue, forward-facing eyes with black pupils, and four, smaller, simple eyes sitting in a 2x2 pattern on its forehead. It has two long pedipalps connected from the underside of its head, which are blue and hairless on their lower half and covered in thick yellow fur on the upper half. Galvantula's body is covered in yellow and light purple fur on top with blue fur under its abdomen. Four tufts of hair sprout from under its abdomen and grow upward. Two large tufts sprout from the left and right of the rear, while two smaller ones sprout from each side. The fur on its back is light purple and with three thick, yellow stripes running up from its rear. Despite being based on a spider, Galvantula has only four legs. Each leg is connected to the head by a blue upper half. The lower half is covered in yellow fur and forms a bell-shape over its blue, conical feet.
Galvantula likes to use electrically charged silk to ensnare prey. Galantula preys on the chicks of bird Pokémon that cannot fly, by placing electrified threads near the nests. Galvantula attacks its foes with electricity by using the fur located on its abdomen. The electricity stuns the victim which can last three days and three nights. This allows Galvantula to consume the target at its leisure. Its pedipalps are very strong, allowing Galvantula to hold down unruly prey. It also uses electric webs to defend itself from threats. As seen in the anime, Galvantula is not particularly aggressive unless provoked. If bothered, it may attack in groups. It has been shown to be extremely caring and protective of its pre-evolution, Joltik, and will aggressively find ways to help it.
In Crisis at Chargestone Cave!, multiple Galvantula and Joltik were residents of Chargestone Cave, where they fed off on its electricity. However, they began stealing electricity from Pokémon and objects to feed on because the rocks in the Chargestone Cave that they normally fed on were being stolen by Team Rocket. They reappeared in a flashback in Battling the Bully!.
In Team Plasma's Pokémon Power Plot!, Colress used a Galvantula as a test specimen. It appeared to be one of Colress' favorites, as he called it his "star test subject", but it passed out when Colress attempted to increase the intensity of the EM waves. After it recovered, it was forced to fight Pikachu and Axew. It was eventually released from Colress's control when Team Rocket stole his data and deactivated the machine.