Those familiar with the Sega’s last pre-needlemouse “traditional” Sonic the Hedgehog title remember it’s big selling point – the Knuckles “Lock-On” feature, that allowed gamers to play as the feisty red Echidna in both Sonic 2 and 3.  Despite being left out of “Sonic’s Gensis Collection on PS3 and 360, Nintendo’s Virtual Console Release retains the feature for gamers who previously purchased the other titles.
From the Press Release:
This game features Lock-On Technology, which allows you to play as Knuckles in other Sonic titles available for the Virtual Console, including Sonic The Hedgehog 2 and Sonic The Hedgehog 3, as long as these titles are part of your Virtual Console library.
Although this feature is also present for Xbox Live and PSN versions of Sonic & Knuckles, it nonetheless an awesome addition to the VC, and a neat feature that adds a ton of replay value to Sonic 2 and 3. Â If you’re a classic hedgehog fan, be sure to check it out.