C#

object[] arr2 = new object[]{null, "leppie", null};
...
void Foo(Array arr)
{  
  arr.SetValue("blah", 0);
  //the last element "mysteriously" becomes "" and does not stay null
}

Array chararrarr = Array(typeof(char[]), 2);
chararrarr.SetValue( "blah".ToCharArray, 0);
chararrarr.SetValue( "blep".ToCharArray, 1);

char[][] carar = (char[][]) chararrarr;
//cast explosion here

class TheBase
{
  public event EventHandler MyEvent;
 
  protected virtual void OnMyEvent(EventArgs e)
  {
    if( MyEvent != null )
    {
      MyEvent(this, e);
    }
  }
}
 
class TheDerived
{
  protected override void OnMyEvent(EventArgs e)
  {
    if( ShouldFireMyEvent )
    {
      base.OnMyEvent(e);
    }
    else
    {
      // the MyEvent event will not be fired
    }
  }
 
  public void FireMyEvent()
  {
    // CAUTION: Fire MyEvent only if the code using this event is guaranteed
    // not to break because the Event was fired outside of its normal usage.
    //
    // IOW, if several events fire in a sequence, you must fire all of them
    // in that sequence.  Also don't fire this event yourself if you have
    // other means of doing so (such as calling Invalidate in a Windows
    // Forms Control instead of firing the Paint event yourself.)
    OnMyEvent(EventArgs.Empty);
  }
}