Deposit Dispute - Bogus Charge?

So here's what has happened.

I was a tenant at a unit for 12 /mo's at which time I remained in communication with the property management extensively whenever a situation arose. This includes when I added my 3 week old Shih Tzu puppy and added someone onto the lease mid-year. I've never been late on any payments and have had no complaints from the management company or my neighbors.

I ended up giving my notice to vacate in a proper manner and requested my deposit be refunded. I was expecting the normal cleaning costs we both agreed upon. However, what I received was far from that. The only additional cost would have been for my puppy scratching one of the bedroom doors which would need to be repaired and I take full responsibility for.

Move Out Statement
Item in Dispute: "Pet, Unauthorized - Kitten observed in unit (Lease: 4.8) $500.00 Charge

I've never had any other animal on the property other than my dog. Note, the date they created the charge was when they performed a move out inspection. No where in the things they sent me did it state what was observed or by whom. I've always heard companies try and do these types of things and create bogus charges but I've never experienced it until now. I've always had great relationships with my property management companies.

On the first page it says "Any disputes must be submitted in writing", "Any balance shown on the last page of your statement is due upon receipt", and "Any un-paid amounts are promptly turned over to collections".

I immediately sent them an e-mail and drafted up a written notice I'm going to be sending once I get a chance to print it out. My concern is that they will come back saying it must have been a cat who damaged the door or something crazy.

I've also sent a request for consultation to a lawyer who's helped me out previously to see what his thoughts are on the matter. If I take this to Small Claims Court do I have a chance? They will have no photos of such "kitten" as there never was one and if their claim is that It's because of the scratches on the door It's because I had a dog which I paid a deposit for.
They did say I need to pay $150.00 after they charged me $500.00 plus other charges for carpet cleaning etc and taking my deposit of $800.00
@Flower - I don't think you read my question fully; at no time did I ever violate my lease. The roommate was added to the lease prior to him moving in meaning the property management gave authorization. The scratch on the door is from the dog and does not justify a $500.00 penalty fee for having an unauthorized "kitten" on the property as there has never been any other animal on the property besides mine which was added onto the lease. This is all in my question please read fully before answering.