Get a bird with the jjbird code or from a cage.
Have it kill any enemy in any level Then, enter jjbird
as a code for it to go away. When it leaves the screen, switch
to any other weapon and shoot at anything on the screen. Then,
enter the jjbird code again. One bird will appear from
one side, then two or three seconds later, the original bird will
return. You might not be able see it. However, if you look closely
you can see two birds' wings flapping. This may require some practice.
You will have to do this every time you want two birds.
Published strategy guides
Trainer