Dr. Mario & Puzzle League doesn’t have a real time single-pak multiplayer mode. Instead, a downloadable trial demo version of either Dr. Mario or Puzzle League can be sent to an open GBA and played until the power turns off.
Dr. Mario is like the NES version but with updated visuals and less music options whereas Puzzle League is loaded with options and features. Pretty cool if you ask me. There is even a Sleep Mode option so you can keep the program stored in your GBA for longer.
This is Single-Pak link!