It’s green, oddly shaped, and seems to have a plant growing on its back. Bulbasaur, the Seed Pokemon, is the first Pokemon listed in the National Pokedex and is also the Kanto region’s grass-type starter. Because Bulbasaur is the first entry in the National Pokedex, by default it is automatically the first grass-type, poison-type, dual-type, and starter Pokemon in the National Pokedex order. Bulbasuar is also the only dual-type, unevolved starter.
According to its pokedex entries, it was born with the bulb on its back and can store enough energy there to last it days without needing food. As it grows, so does its nutrient-filled bulb. Bulbasaur tend to like soaking up the sun’s rays, which also helps its bulb grow. Bulbasaur’s name seems to come from the words ‘bulb’ and ‘dinosaur’, though the word ‘saur’ is actually Greek for “lizard”. Appearance-wise Bulbasaur looks somewhat similar to a frog or toad, though it’s also been speculated over whether or not it could also be based on some form of Dicynodont – a sort of mammal/reptile creature that lived in the Permian period (which would explain its toes). Unlike amphibians, though, Bulbasaur has ears atop its head.
Once Bulbasaur reaches level 16, it evolves into Ivysaur and the bulb on its back begins to bud. Ivysaur is the only middle evolution of a grass-type starter to be a dual type Pokemon. It is also the only Generation I Pokemon whose name begins with the letter ‘I’. Out of all the Kanto starter middle evolutions, Ivysaur evolves the soonest (at level 32) and is actually the first evolved Pokemon in the National Pokedex. Like its pre-evolution, Ivysaur’s design seems to be based off from frogs and toads though can also be based off from the Dicynodont. It looks very similar to Bulbasaur, just slightly larger with teeth and a budding flower on its back. Its name seems to come from the words ‘ivy’ and ‘dinosaur’.
And finally, once Ivysaur reaches level 32 it evolves into Venusaur. Venusaur is quite a bit larger and has a fully bloomed flower on its back resembling the Rafflesia. Venusaur is the first fully evolved Pokemon in the National Pokedex, as well as the first one to have a gender difference. Throughout the game generations, Venusaur and its pre-evolutions have undergone quite a few changes in their sprite color-scheme. Originally, their skin was a vibrant green (which could be because of the color limitations in the Gameboy and Gameboy Color), which changed to a more tealish color, which was again adjusted to a more blue shade to match its anime counterpart. Also, Venusaur’s sprites in Red, Blue, and Green had darker spots of blue similar to Bulbasaur’s and Ivysaur’s, though they were later changed to warts. Venusaur’s name most-likely comes from the words ‘venus’ (probably to reference a Venus Flytrap) and ‘dinosaur’. Considering its warts, Venusaur resembles more of a toad. Its design could also be based off from the Dicynodont too.