On the V4? Take a look at this Growth Chart
Here.
It explains all. (Your tamagotchi must be a boy)
To get Androtchi, you must have a teenager Young Mametchi, or Young Androtchi, make sure they're Fashion (Star Icon) points is the highest among the other icons.
To get Mametchi make sure you have Young Mametchi, or Young Androtchi, then make sure they're Intelligence (Pencil Icon) points is the highest among the other icons.
Just don't feed your tamagotchi overly to much, neglect it, or have it to LOW in skill points. Or you might get a universal character..
Flag game = Increases the Flower Icon points.
Shape Game = Increases the Pencil Icon points.
Dance Game = Increases the Star Icon points.
Jump rope & Mimic randomly increase points in any area.
-Locky458