A Cat Cleric was a leader and/or teacher in the old religion (worship of Cloister) of the Felis sapiens, a sentient yet primitive humanoid species which had evolved from Frankenstein's litter aboard Red Dwarf.
When the cats left Red Dwarf on the Cat Ark, they left behind only a few behind such as the sick, lame and uncool. These included The Cripple and The Idiot, who would go on to have a child together in Cat.
They were ministered over by an old blind Cat Priest in an old chamber in Supply Pipe 28, who took on the Cat as his ward. However, towards the end of his life he had began to lose his faith. He was eventually discovered in his final minutes by Dave Lister, who pretended to be Cloister, giving the Cat Priest peace before his end. ("Waiting for God")
The Promised Land
The remaining cats travelled the Galaxy in the Cat Fleet, which some thirty years later had come under the tyrannical of the Feral Cats under Rodon. Rodon had declared himself a 'living god' and outlawed Cloister worship, punishable by death.
The three clerics searched for Red Dwarf so that they could ask for Cloister's help in liberating the Cat people. However, they were not able to find Red Dwarf, and took refuge in Iron Star, where by chance they are eventually found by the boys from the Dwarf, confirming their beliefs that Lister is Cloister. When Lister refutes this, they just say that he is being humble.
Eventually, after being returned to the rest of the cats, and having being liberated by "The Mighty Light" - actually a superpowered Arnold Rimmer - they changed their religion to worshipping Rimmer instead of Lister. The Cats started drawing 'H's on their heads like Rimmer, and all the other cats seemed to join in. As the Cat Fleet flew off, the ships also formed a "H". Rimmer said that being a god will look great on his CV. (The Promised Land)
- Although they depicted doughnuts and holy custard stains, the Cat Priest's robes were still quite regal. He may have been akin to a an 'archbishop'.
- The last three Cat Clerics (Sol, Luna and Peanut) dress like Lister in leather jackets and ushanka hats all covered in badges, even having cigarettes hanging out of their ears much like Lister did in earlier series. Luna also claims that she spent her life eating three vindaloos a day in honour of Cloister/Lister.