The latest release of Illustrator CC 2015 introduces Dynamic Symbols, which lets you create multiple instances of a master symbol that retain their link to the master symbol even when their shape and visual attributes are altered.

This relationship lets you make fundamental changes to the master symbol that are automatically applied without undoing any previous changes to the individual instances of the symbol.

You can now change the shape and visual attributes, and apply transformations to individual symbol instances while they remain dynamically linked to the master symbol, saving time to create and perfect your artwork.

Go to Window > Symbols to open the Symbols panel. Drag a marquee around your graphic with the Selection tool making sure all components of your artwork are selected; then drag the graphic into the Symbols panel. 

In Symbol Options, give your symbol a descriptive name; we named it Dog in our example. Choose Dynamic Symbol as the Type and click OK. A new thumbnail appears in the Symbols panel with the "+" symbol showing it is Dynamic.

To place an instance, select its thumbnail in the Symbols panel and click Place Symbol Instance. You can also simply drag the thumbnail from the Symbols Panel to your artboard, or duplicate the symbol directly from the artboard.

Place a few instances. You can scale, rotate, reflect, and skew symbol instances as needed without breaking their link to their master.

You can also change several visual and shape attributes of a Dynamic Symbol instance without breaking its link to the master symbol. Thus an instance may have a different stroke, fill, opacity, and effect than its master symbol.

First deselect all artwork, and then select parts of the Symbol with the Direct Selection tool. Change its stroke and fill colors, or add a gradient or pattern fill, or an effect such as a drop shadow.

Note: You cannot perform some operations such as editing live text inside a Dynamic Symbol; and scaling, moving, or deleting elements of a Dynamic Symbol. 

Any shape manipulations you make to the master symbol will be automatically applied to its instances. 

Select any instance of a symbol and click Edit Symbol in the Control panel. 

Use the Direct Selection tool to alter a path's shape. You can also reposition objects within the symbol.

Click the arrow at the top of the window to return to your artwork. The changes you make are applied to all instances of the symbol while leaving their unique visual appearances intact.

Note: If your master symbol uses a Live Shape, any edits to the shape's properties—such as corner type—will be reflected in symbol instances. 

You can always reset an instance to its default size and appearance.

Select the instance, and then click Reset in the Control Panel.