Frog newbie = Frog.Create();
newbie.legs.append( FrogLeg.Create() );
newbie.legs.append( FrogLeg.Create() );

Frog frog = newbie;
frog.legs.append( FrogLeg.Create() );
frog.legs.append( FrogLeg.Create() );
frog.gill = FrogGill.Create();