From Wikifang, a definitive guide to Telefang, Dino Device and Bugsite
Fusion evolution (Japanese: 改造進化, kaizou shinka; Bootleg: reform evolution) is one of the methods of evolution in the Telefang series. It is done by fusing the correct items with the respective Denjuu. Unlike Natural evolution, Fusion and Lab evolution can be carried out regardless of the Denjuu's level.
Fusion-evolved Denjuu generally have weaker stats than naturally- or lab-evolved Denjuu.
 Fusion Evolution in Telefang 1
In Telefang 1, the player can obtain fusion evolution items by buying them from shops, finding them in treasure chests, or receiving them from a person. To fuse items with Denjuu, the player must talk to the Gumi in the bottom left of certain shops throughout the game. Towns with shops that offer fusion evolutions include Kurinon Village, Freesia, Barran, Panses Village, and Tripa Village.
 Fusion Evolution in Telefang 2
In Telefang 2, fusion evolution items can be randomly found after winning a battle. The player can then fusion-evolve Denjuu by fusing them with their respective items in a fusion building.
 Differences in fusion evolution between Telefang 1 and 2
In Telefang 1, fusion evolution is permanent, but it is reversible in Telefang 2.
Telefang 1 also requires use of a specific item which differs depending on the Denjuu involved - for example, Cryptoride requires a Bazooka to evolve into Cryptoarm. In Telefang 2, all fusion items are assigned a habitat type and any of them can be used to evolve a Denjuu into the item's respective type, if it has such an evolution - for example, Penelope (Basic) could use a Squirt Gun or Washer to evolve into Penelope (Aquatic), as both items are classified as Aquatic-type. The resulting evolution's stats may differ depending on the item used, however.
In addition to this, all fusion evolved Denjuu in Telefang 2 change their type. This also effects recurring Denjuu species from Telefang 1 - for example, in Telefang 1, Grassland-type Beebalm fusion evolves into Grassland-type Easydog. In Telefang 2, Grassland-type Beebalm fusion evolves into Desert-type Easydog.