casting fails!

Consider the following C# classes:

1. namespace Something.Models
   {
      public class Cat
      {
         public int Lives { get; set; }
         
         public Cat()
         {
            Lives = 9;
         }
      }
   }
    
2. namespace Something.Models
   {
      public class BakersCat : Cat
      {
         public BakersCat()
         {
            Lives = 13;
         }
      }
   }
    
3. using Something.Models;
   namespace Something.Utilities
   {
      public static class Killer
      {
         public static Cat Kill(Cat cat)
         {
            cat.Lives = cat.Lives - 1;
            return cat;
         }
         
         public static void Kill(ref Cat cat)
         {
            cat.Lives = cat.Lives - 1;
         }
      }
   }

 
 

Well this won't work...

BakersCat muffin = new BakersCat();
muffin = Killer.Kill(muffin);

 
 

...and this won't work either!

BakersCat cookie = new BakersCat();
Killer.Kill(ref cookie);