Sonic_knuckles_wsonic3

The S&K cartridge contained a passive pass-through slot. When a second cartridge (S3) was inserted:

The union enabled the unique playstyles of both characters across the entire combined map. sonic_knuckles_wsonic3

Without specific details, here are a few possibilities: The S&K cartridge contained a passive pass-through slot

Technical & Gameplay Integration Analysis of Sonic & Knuckles + Sonic the Hedgehog 3 (Lock-On Technology) it remains a case study in:

The S3 + S&K lock-on configuration is widely regarded as the first successful "episodic DLC" of the pre-internet era. It transformed two $60 games into a single $100+ experience without requiring a new cartridge. For modern retro developers, it remains a case study in: