Tyrannosaurus Rex is a mutation. You can catch one of the stories in Pokemon Golden Heart/Silver Spirit! If you want the rest, go fishing for carp, but you must catch golden carp, which is also mutated, and then raise it to level 20 and evolve into a red Tyrannosaurus Rex. In fact, the ability of flash pet (that is, mutation, which we call flash pet) is the same as that of general pet, so unless you love it especially, there is no need to catch it deliberately, because the probability of encountering flash pet is very low, and you don't have to be depressed if you don't catch it. Pokemon Magikarp can't evolve into a red Tyrannosaurus Rex. Normal Magikarp will evolve into a blue Tyrannosaurus Rex at level 20. Red Tyrannosaurus Rex refers to the twinkling elves. Flash Pokemon refers to a Pokemon whose color is different from other normal elves of the same kind. Tyrannosaurus Rex and Lake of Wrath were transformed by rockets, and they were bound to flash. The color was red, and the personality and individual value were randomly selected.