From The TimeSplitters Wiki

Introduction

It is discovered in TimeSplitters: Future Perfect, that the zombies (at least the zombies in 1994) were actually created by Jacob Crow and The Brotherhood of Ultra Science, in his attempt to become immortal. Zombies, such as the shock zombies (which could fire electricity) in particular were early 'prototypes' for the TimeSplitters.

Varieties

Generally, in the games zombies are undead. Often times zombies are confused as characters who have risen back from the dead. There are a variety of zombies, usually depending on their location and way in which they were created. Zombie types are as follows:

• TimeSplitters
  • Brown Zombie
  • Girl Zombie
  • Green Zombie
  • Jacket Zombie
  • Police Zombie
  • Skull Zombie
• TimeSplitters 2
  • Crypt Zombie
  • Feeder Zombie
  • Sewer Zombie
  • Undead Priest
• Military Zombies
  • Capt. Pain
  • Lt Chill
  • Private Poorly
  • Sgt Slate
  • Trooper Grey
• Undead Mutants
  • Hybrid Mutant
• Others
  • INFO NEEDED

Special Note

Although it may be true that Jacob Crow created zombies, they can also be necromanced by dark people such as Jacque de la Morte. In addition, it appears that Timesplitters pocess a "evil aura" that can mutate or zombify people.