If a game with a cartridge's memory size larger than 2MB is attached, the console will not run the lock-on game but booting up the standalone Sonic & Knuckles game instead. 
The Sonic & Knuckles cartridge usually reads the second half of the attached ROM. As the ROM header is placed in the first half of the attached cartridge, it will not recognize it as a valid game. 
7/7
If the player inserts almost any other Mega Drive cartridge into the slot adapter, again a screen with Sonic characters and a scrolling text "No Way" appears. 
This time after pressing the A, B and C button at the same time the player gets to play only a single Special Stage without the password ability based on the serial number of the cartridge's ROM header data. 
6/x
"I wanted to introduce a new kind of fear into the game, a persistent feeling of paranoia.
The Nemesis brings that on in spades.
When it disappears after the first confrontation, you live in constant dread of the next attack.
The idea is to make you feel like you're being stalked."
- Shinji Mikami, Resident Evil 3 producer, 2000
Attaching Sonic 1 to Sonic & Knuckles unlocks the Blue Sphere mini game, a collection of Special Stages in the same style of those in Sonic 3 & Knuckles. 
After starting the console a screen with Sonic characters and a scrolling text "No Way" appears. 
While this screen is visible, pressing the A, B and C button at the same time opens the Blue Sphere menu. 
Blue Sphere has 134,217,728 levels and a password feature.
5/x
"If the player isn't tricked into believing that the world is real, then there's no point in making the game.
If you can captivate the player without having to trick them, then the game is worthwhile."
- Hideo Kojima, 1998
If you attach Sonic 2 to the Sonic & Knuckles lock-on this unlocks "Knuckles the Echidna in Sonic the Hedgehog 2", wherein the player can play the game using Knuckles and his abilities.
Using these special moves, Knuckles can explore areas inaccessible with Sonic or Tails, where secrets such as extra monitors have been added. 
4/x
Sonic & Knuckles has a lock-on feature that allows players to open the hatch on top of the cartridge and insert a second one.
When Sonic 3 is inserted, the player can play through both games as one, the originally intended Sonic 3 & Knuckles. 
This features several changes to the games, such as slightly altered level layouts and the ability to play through both titles as Knuckles or Tails. 
3/x
Sonic & Knuckles was developed in 1994 simultaneously alongside its predecessor, Sonic the Hedgehog 3. 
Both titles were planned as a single game until time constraints and cartridge costs forced the developers to split it. 
Therefore their gameplay is similar.
Both are 2D side-scrolling platformers with similar level design, graphics and game mechanics.
Unlike in Sonic 3, in Sonic & Knuckles the player chooses either Sonic or Knuckles to play.
2/x
This will be a thread about Sonic & Knuckles for Sega Mega Drive/Genesis and its cartridge's Lock On feature.
There is much to say about the game's background and the possibilities of the Lock On feature in regard to other games, especially the console's Sonic titles. 
1/x
...pinball game, Sonic Pinball Party, was released in 2003 for the Game Boy Advance and re-released in 2005 in compilation collections with Sonic Advance, Sonic Battle, and Columns Crown.
#RetroTrivia about the game consoles of our childhood
...characters and an all-female main cast. The game is also one of the few entries to have multiple possible endings.
#RetroTrivia about the game consoles of our childhood
...3D polygon graphics.
The developers chose this technique because having full 3D graphics would not allow them to create graphically rich and detailed environments. 
#RetroTrivia about the game consoles of our childhood
...critics, later games were less well received. 
The first 4 video games in the series, SH, SH 2, SH 3 and SH 4: The Room, were developed by an internal group called Team Silent, a development staff within former Konami subsidiary Konami Computer Entertainment Tokyo. 
The later 6 games, Origins, Homecoming, Shattered Memories, Downpour, Book of Memories and P.T. (a Silent Hills playable teaser), were developed by mostly Western developers. 
...third-party support. 
The game was ported to the PlayStation 2 in 2005 after Capcom stated that it did not fall under the exclusivity deal with Nintendo. 
#RetroTrivia about the game consoles of our childhood
...Luigi must travel around the world to find and return stolen treasures as part of a quest to find his brother, Mario, who has been captured by Bowser. 
#RetroTrivia about the game consoles of our childhood
#RetroTrivia about the game consoles of our childhood
...Konami of America senior vice presidents discomfort with the religious connotations of the title Akumajō Dracula, which he believed translated as "Dracula Satanic Castle". 
#RetroTrivia about the game consoles of our childhood
...The shown Marvel vs. Capcom: Clash of Super Heroes debuted in arcades in 1998. 
Ports to the Dreamcast and PlayStation soon followed in 1999.
Rather than strictly using Street Fighter characters, the game included characters from other Capcom video game franchises, such as Mega Man, Morrigan, and Strider Hiryu. 
...to showcase the Game Boy until Nintendo of America bundled Tetris. 
Trivia about the game consoles of our childhood
...The authorities stated that the word Ninja doesn't fit into a comic series for children. 
