The Pokémon series has let the player perform in-game trades with NPCs in the past, but not all of these deals are worth taking, as the player will be left with a worse Pokémon than the one they sent off. It's possible to trade Pokémon with other players, which can even lead to the series' Pokémon trade evolutions, yet there are always a few in-game trades in the mainline series entries, some of which were necessary for completing the Pokédex in Pokémon Red and Blue, as this was the only way to obtain Pokémon like Jynx and Mr. Mime. The in-game trades could also offer Pokémon that would make certain encounters easier, like the Onix in Pokémon Gold and Silver, as it can be used to beat Falkner and Whitney.
The in-game trades in the Pokémon series have the same benefits as trading with a human player, allowing them to receive more experience points in battle. The majority of the in-game trades include Pokémon that the player has access to in other areas of the game, but that extra experience point gain can make them a better choice, especially if the player is just looking for Pokémon to complete the single-player content in each game. The traded Pokémon can evolve through trade and through held items, which also allow the player to acquire rare gear or additional restorative items. The rare items include things like Mega Stones, Z-Crystals, and gear used for trade evolutions.
In a lot of cases, the player won't bother with an in-game trade, unless they happen to have the Pokémon needed for the trade to hand, and it's not being used as a party member. There are some amazing in-game trades in the Pokémon series, but others should be given a wide berth. Not all Pokémon trades are equal and the player can be scammed by some of the worst Pokémon trades in the series.
The Gyarados For Magikarp Trade In Pokémon X & Y
Magikarp might be the most easily accessible Pokémon throughout the entire Pokémon series, as it can be caught with every type of fishing rod, and is commonly encountered when surfing. The only mainline Pokémon games where Magikarp cannot be encountered in the wild are Pokémon Black and White, though they can be purchased for five hundred Pokémon Dollars a pop from a salesman on the Marvelous Bridge. This only accounts for the Gen V games, as Magikarp are common everywhere else in the Pokémon world.
Someone didn't mention this fact to the Hiker who visits the hotels in the Kalos region in Pokémon X and Y. The hotels in Kalos will have different guests on different days, depending on the calendar set by the in-game clock. If the player manages to meet the Hiker guest, then he will offer to trade his level five Magikarp for a Gyarados, which is the evolution of Magikarp. There is nothing special about this Magikarp and it's likely that the player will have had chances to catch one already for free, without needing to give up a better Pokémon in the process. It's likely that this trade is intended as a joke, aa the Magikarp's name is Carpe Diem, which refers to seizing the moment without putting too much thought into it, while also being a pun regarding carp.
The Bagon For Horsea Trade In Pokémon Emerald
The Dragon-type Pokémon used to be among the rarest in the series, as there were only a handful of them in existence, and they were usually a pain to catch. This changed over time, as the introduction of overpowered Fairy-type Pokémon in Pokémon X and Y offered a hard counter to Dragon-types, while the enhanced online features used by the Nintendo 3DS also made it a lot easier to trade with players online, so Dragon-type Pokémon became more plentiful. In the old days, players had to struggle to catch Dragon-type Pokémon, and Pokémon Emerald was no exception.
Gen 3 introduced the Salamance line, which introduced fresh Dragon-type Pokémon to the series. In order to catch Bagon, the first Pokémon in the Salamence line, the player had to travel to Meteor Falls, where it would appear in one specific area, and was easy to miss, if the player didn't know where to look for it. If the player travels to Pacifidlog Town, then they can trade one of their precious Bagon for Horsea. The reason this trade is so bad is that Horsea can be found in the routes near the town, by using a Super Rod in the waters, making it a lot easier to catch than a Bagon.
The Mean Everstone Haunter Trick In Pokémon Diamond & Pearl
The trade evolution Pokémon were the bane of Pokémon fans that didn't have any friends who were into the franchise or were playing the games on an emulator, as they made it impossible to complete the Pokédex. Pokémon like Alakazam, Gengar, Golem, and Machamp were forever beyond the reach of those without a link cable, meaning that some of the best Pokémon in Pokémon Red and Blue just couldn't be caught, no matter how hard the player searched. The Pokémon series continued to add trade evolution Pokémon over time, but online trading meant that it became a lot easier to acquire them.
None of the in-game Pokémon trades will help the player out, even though one seems like it will. In Pokémon Diamond and Pearl, there is a trainer in Snowpoint City who will offer to trade their Haunter for a Medicham. This is an amazing deal, as Meditite can be found all over Sinnoh and they can be evolved into Medicham. If the player trades for a Haunter, then that means it should evolve into a Gengar upon receipt. It turns out that this deal is too good to be true, as Game Freak decided to play a cruel trick on the player with this trade. The Pokémon Diamond and Pearl Haunter will not evolve when it arrives in the player's party, as it was sent over while holding an Everstone, preventing it from evolving. There also isn't any value in owning the Haunter, as Gastly can be found all over Sinnoh. Game Freak was clearly fond of this jape, as it reappeared in Pokémon Brilliant Diamond and Shining Pearl. Snowpoint City had the chance to contain the best in-game trade in the Pokémon series, but it turned out to be a joke at the player's expense.