Actually, that connection is from the spaceworld (or E3?) where they announced Gamecube and GBA. As you can see from the window on the Gamecube's disc door, and the GBA's colors, the system's weren't fine-tuned yet. The big grey chunk was definately added when Nintendo realized that the cord would easily pop out and ruin a GBA/GCN connection. If you don't own one, all the connector does with the extra bulk is hook into the top of the GBA.