[XAML]
<Popup IsOpen="{Binding
ElementName=myCheckBox,Path=IsChecked}"
PlacementTarget="{Binding ElementName=myCheckBox}"
AllowsTransparency="True"
PopupAnimation="Slide"
HorizontalOffset="50"
VerticalOffset="50"
>
<!--The Margin set on the Canvas provides the additional
area around the Popup so that the Popup is visible when
it rotates.-->
<Canvas Width="100" Height="100" Background="DarkBlue"
Margin="150">
<Canvas.RenderTransform>
<RotateTransform x:Name="theTransform" />
</Canvas.RenderTransform>
<TextBlock TextWrapping="Wrap" Foreground="White">
Rotating Popup
</TextBlock>
</Canvas>
</Popup>