First, be aware that the following does not matter:1) That you never had issues  with previous landlords--that literally has no bearing whatsoever on this case;2) That the ceiling also leaked--IF you car caused "damage" (a cat urine smell) which requires replacement, you may be charged for that cost, even if there was other damage from other causes as well.In line with 2), what really is key is whether something you (or you cat) did required the repairs made; if so, it properly is something the landlord can look to recover from you. (Other damage *may,* depending on circumstances, provide a basis for reducing or discounting what you are charged--but is seems as if the landlord is doing that anyway.)If you don't pay voluntarily, the landlord's options are to sue you, or, when you move out, to take the cost from your security deposit, which is something he or she can almost certainly do if he or she can document the damage and the cost to repair.