The most likely explanation is that the trainer has been given a reward, for defeating a gym leader, winning a contest or shining in a Team Rocket event.
Level Ups do just what you might expect and are only given out when trainers have excelled in an event or after winning a gym badge, contest ribbon, pokéringer ring or sumo belt.
Evolution Tokens are given out to badge- and ribbon-winners, and entitle the trainer to evolve one of their pokémon by one stage. The tokens can be used at any time after being rewarded, and can be used on any pokémon in the trainer's possession.
- Rare Pokémon are sometimes offered as a reward to those who show outstanding skill, quick-thinking, unshakable determination and abounding compassion while fighting Team Rocket. If you are offered a rare pokémon you can either accept it and take it into your party, or politely decline it and receive an Evolution Token instead. But we don't accept returns and we offer no refunds. Your first decision is final.
Revives are usually handed out as runner-up prizes, or in recognition of a noteworthy performance. A revive can be used in a trainer battle, a gym battle or a Team Rocket event. When making use of a revive you must decide which pokémon you wish to use it on before you enter a battle. You must then add a duplicate of that pokémon to the last slot in your party, before you enter the battle. A revive only counts as being used once the duplicate pokémon makes a move and once it has been used it cannot be reused. (More info here)
Rare Candy are much like revives; they can be used only once and only in a trainer battle, gym battle or Team Rocket event. With one of the yummy confections in your possession you can increase the level of one of your pokémon by five (to 55), to aid you in one fight. The effect does not stack if more than one Rare Candy is used on the same pokémon. Furthermore, a rare candied pokémon that is revived does not keep its bonus five levels.Other rewards will be added here as and when we think of them. If you have any ideas, post them in the general chat thread for consideration.
