This is possibly "by design" (i.e. I don't know) but I've noticed that if I reparent a Silverlight control from one Canvas to another then its Loaded event fires for a second time when it is reparented.

So, with a user control such as;

  public class UserControl1 : Control
  {
    public UserControl1()
    {
      System.IO.Stream s = this.GetType().Assembly.GetManifestResourceStream("SilverlightProject6.UserControl1.xaml");
      this.InitializeFromXaml(new System.IO.StreamReader(s).ReadToEnd());

      this.Loaded += new EventHandler(UserControl1_Loaded);
    }

    void UserControl1_Loaded(object sender, EventArgs e)
    {
      
    }
  }

with a XAML definition of;

<Canvas xmlns="http://schemas.microsoft.com/client/2007" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        Width="640"
        Height="480"
        Background="White"
        >

</Canvas>

if I then have a Page that uses this as in;

<Canvas x:Name="parentCanvas"
        xmlns="http://schemas.microsoft.com/client/2007" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        Loaded="Page_Loaded" 
        x:Class="SilverlightProject6.Page;assembly=ClientBin/SilverlightProject6.dll"
        xmlns:ctl="clr-namespace:SilverlightProject6;assembly=ClientBin/SilverlightProject6.dll"
        Width="640"
        Height="480"
        Background="White"
        >

  <Canvas x:Name="c1" Canvas.Left="0" Canvas.Top="0" Width="50" Height="50" Background="Red" MouseLeftButtonUp="OnMouseDown">
    <ctl:UserControl1 x:Name="ctl1"/>
  </Canvas>
  <Canvas x:Name="c2">
    
  </Canvas>

</Canvas>

and some code that does the re-parenting;

  public partial class Page : Canvas
  {
    public void Page_Loaded(object o, EventArgs e)
    {
      // Required to initialize variables
      InitializeComponent();
    }
    private void OnMouseDown(object sender, MouseEventArgs args)
    {
      this.c1.Children.Remove(this.ctl1);
      this.c2.Children.Add(this.ctl1);
    }
  }

then I find that at the point where I move the control from the c1 Canvas to the c2 Canvas the Loaded event on the control fires for the second time.

As I say, that may well be "by design" as I can see why you might want to know about such a big event in your lifetime as a control but it's worth being aware of.