Krispies were once of Dave Lister's favorite foods, along with curry, beer and beer milkshakes. Lister kept large stocks of Krispies in his locker in his sleeping quarters aboard the JMC mining spaceship Red Dwarf.
It is unknown if the cereal was ship-issue, or had been purchased by Lister whilst on planetary shore leave on Titan, Mimas or Miranda. Lister smuggled an unquarantined animal aboard, a pet cat named Frankenstein, which broke Space Corps Directives. Lister kept the animal hidden in his sleeping quarters, feeding the cat his milk ration and Krispies.
Three million years after the accident which killed the crew, Holly revived Lister from stasis. Upon encountering the Cat for the first time, Lister was able to get the Cat to come into the sleeping quarters and sit down by offering him Krispies. The Cat loved them so much as to start singing a song about them. Thus it was Krispies that first enticed the Cat to join the boys from the Dwarf. (Pilot episode)
Afterwards, the Cat could often be seen eating Krispies, especially in Series I. When Lister went looking for Cat in Supply Pipe 28, he tried to lure Cat back by shouting that his Krispies "are getting warm". ("Waiting for God")
Krispies may be related a confectionery bar, the crispy bar.