Animal a;
if( happyDay() )
    a( "puppies" ); //constructor call
else
    a( "toads" );

Animal a(getAppropriateString());

Animal a(happyDay() ? "puppies" : "toads");

char *AnimalType;
if( happyDay() )
    AnimalType = "puppies";
else
    AnimalType = "toads";
Animal a(AnimalType);

auto_ptr<Animal> p_a;
if ( happyDay() )
    p_a.reset(new Animal( "puppies" ) );
else
    p_a.reset(new Animal( "toads" ) );

// do stuff with p_a-> whatever.  When p_a goes out of scope, it's deleted.

Animal& a = *p_a;

// do stuff with a. whatever

Animal* a;
if( happyDay() )
    a = new Animal( "puppies" ); //constructor call
else
    a = new Animal( "toads" );

// ...
delete a;

class Animal
{
public:
    Animal(){}
    void Init( const std::string& type )
    {
        m_type = type;
    }
private:
    std:string m_type;
};

Animal a;
if( happyDay() )
    a.Init( "puppies" );
else
    a.Init( "toads" );

void body(Animal & a) {
    ...
}

if( happyDay() ) {
  Animal a("puppies");
  body( a );
} else {
  Animal a("toad");
  body( a );
}

struct AnimalDtor {
   void *m_a;
   AnimalDtor(void *a) : m_a(a) {}
   ~AnimalDtor() { static_cast<Animal*>(m_a)->~Animal(); }
};

char animal_buf[sizeof(Animal)]; // still stack allocated

if( happyDay() )
  new (animal_buf) Animal("puppies");
else
  new (animal_buf) Animal("toad");

AnimalDtor dtor(animal_buf); // make sure the dtor still gets called

Animal & a(*static_cast<Animal*>(static_cast<void*>(animal_buf));
... // carry on

Animal a;
if( happyDay() )
    a = Animal( "puppies" );
else
    a = Animal( "toads" );

Animal a;
if( happyDay() )
    a.init( "puppies" );
else
    a.init( "toads" );