It's Christmas Eve 2000 and underneath the streets of New York City, a diabolical plot is moving forward that could spell the end of humanity. It seems that for a long time, an alien race has been living in the sewers of the city and creating human-alien hybrids who are clones of real people. Using their clones, these aliens have been replacing key public figures with their evil twins. The plan is nearing a conclusion as none other than the President is replaced in attempt to plunge the world into war which would leave humanity ripe for alien take-over. 

Enter Johnny Slater, a Secret Service agent who awakens in a body that is not his own.  Escaping execution, he encounters the alien race, which look like the stereotypical bug-eyed greys. It turns out that most of them are peaceful and that one outlaw has enslaved the rest and is determined to rule the Earth.  Aided by the alien resistance, Johnny sets out stop the alien outlaw and save the world.

The entire game takes place beneath the city in a large tunnel complex with seemingly endless levels. While graphically pleasing at first, they quickly lose your interest. The problem here is repetition. Most of the levels look pretty much the same. Johnny goes from metallic room to metallic room, which are connected by dark tunnels with either red or green lighting effects. Enemies are either black suit humans, technicians, or an assortment of mutants. All are blocky and without much animation or variety. While the plot is interesting at first, the lack of solid graphic support weakens it. Sound and music is similarly without emotion. The mostly repetitive soundtrack is offset occasionally by intense battle music when a major enemy is encountered.

Battles are the most ambiguous feature of the game. Johnny always has a gun which he uses to shoot alarm robots and other defensive devices. Sometimes, doing this will reveal hidden heal or boost items. However, the major battle mode is a one-on-one menu driven wrestling match. When an enemy is encountered, the fighting mode is entered and a timed series of actions occur. The player can choose a variety of kick or punch moves which can be powered up by waiting for the power meter to fill. Unfortunately, there is no control over when the enemy attacks you so that while the player waits for the proper moment to attack, the enemy can get in its own attacks. Each attack you can choose to guard, step, or counter. The success rate of these appears random. There's also a special wrestling lock which occasionally allows the enemy to grab Johnny and do a big wrestling move, such as pile-drivers, arm throws, or body slams. Even more rarely, Johnny can also grab the enemy and do his own wrestling moves. 

As enemies are defeated, Johnny will go up in stats and learn new moves which are added to kick, punch, combo, or wrestling. There's even an option to create your own series of combos. The menu driven combat and stat building are really the only RPG elements of the game. As such, they don't work well because the battles can get very repetitive and drawn out as you and the enemy take turns pummeling each other. This is one instance where actual action based combat may have been a better idea. There's also little or no interaction with the environment or other characters, excluding cut-scenes between levels. This is mainly due to the fact that there's really nobody around. Each room has one enemy to fight so the whole game comes down to entering room after room and fighting one enemy at a time to progress. By the end there's little incentive to keep playing because the plot is predictable and there's zero character growth. 

What's even worse is the control. It's bad enough that Johnny runs like a stiff but does he also have to fight like one? The fight scenes are badly in need of more energy rather than "one action at a time" fighting, which serves only to reinforce the boredom of the game. It's also hard to control jumps, especially when trying to jump forward. Quite often, you end up jumping straight up and being shot by the robot alarms as a result. Aiming your gun has to be the worst feature because you can only aim really high or really low. The control stick is so sensitive that its impossible to aim anywhere in between. Thus, aiming your gun is very jerky and adds unnecessary difficulty to the game. 

As if that wasn't enough, the camera could have used a lot more work. Not only is it slow to turn behind your character but sometimes it sets at an angle where you can't even see where you are. The result is the enemies or traps will hit you when you could have easily avoided them.

This game started out as a cinematic RPG for the N64 but ended up as an ambiguous hodgepodge of action-adventure-RPG-wrestling game. It's almost as if the developers really didn't know what they wanted. Taking out the menu combat would have turned this into a pretty good action adventure game but, as it stands, the forced RPG elements dampen what could have been an enjoyable experience.

Konami's take on the adventure RPG is just like its name suggests: a hybrid of many different genres. Obviously, the creators of this game tried to make something original, but somewhere along the line Hybrid Heaven became a mismatch of lots of things none of which came together very well.