For GALAGA on the Namco "Museum vol 1".....
To disable the cpu ships from firing at you... On stage one..
let all the enemy ships enter..do NOT shoot until they have all come out...
then shoot every ship except the first two bees(yellow / blue)
on the left side.. ie( top to bottom ) 2 bees...

After you have isolated the bees..
let them fly around for the next 10-15 minutes...
DON'T SHOOT ONE SHOT DURING THIS TIME...you just have to dodge them..
just wait patiently...
after a while (10-15min) BOTH bees should stop shooting completely...
to make sure let them pass by at least 2-3 times after you notice this...
then kill them.. for the rest of the game ,ALL enemies will shoot...
THIS is an old cheat from over 10years ago...
and its still intact in this ported version....