And you can clone in this game! All you need is another gameboy and a link cable.
1. Link the gameboys up and go to the trade center.
2. One gameboy should have a good/rare pokemon to be traded, and another, a bad or crappy pokemon.
3. Trade those pokemon, and when the Gameboy that is about to recieve the good pokemon displays "WAITING..." Get ready to shut the other gameboy off.
4. When the message disappears, shut the other gameboy off.
Do not unlink the gameboys!. 5. Continue the trade, as usual, and when the gameboy that is recieving the good pokemon recieves it and the message "TRADE COMPLETED" appears, shut that gameboy off
When you turn both gameboys back on, both games should have the good pokemon! Now, you can trade a crappy pokemon to the other gameboy for the good pokemon on the other gameboy.
EX. Say you wanted a 2 pokemon like Charizard with the most powerful fire attacks, but you taught Fire Blast to another pokemon and don't want to buy it (if you can even). So you trade Charizard and Magikarp. When the gameboy that will recieve the good pokemon displays WAITING... and then it disappears, shut the gameboy off that is recieving the Magikarp. Let the other Gameboy continue the trade, and when it displays TRADE COMPLETED turn that gameboy off. Now turn both back on and go back into the trade center. This time, you will trade another Magikarp to get the Charizard on the other gameboy! Make the trade as usual, and now you'll have two Charizards.
RAWR! Who's the Boogie Monster NOW!!! MUHAHAHA