Crystal

Crystal came out a little while after Gold/ Silver, can is the 3rd Johto game. In this game you have the option of genders, unlike those before it.

Other new features include:
Battle Tower near Olivine City
More puzzles at the Ruins of Alph
Pokemon "swarms" introduced
"Odd Egg" received from Day Care Couple. It has a 50% chance of being Shiny. (Wow, that should be in Diamond...)
Dragon's Den events altered
Rainbow Wing can only be obtained once the three legendary dogs have been caught (Erm...why?)
Move Tutor introduced

Have Fun! :)