hello, I live about 7 miles from KMSP and see planes come over the house all the time.for the first time I saw DC9-50 7miles out and the lights flashed on and off several times. not sure what the lights are called but they are on the wings next to the fuselage. any answers as to why they do that would be appreciated. thanks!! 
Those are most likely the landing lights and often pilots who know that a traffic advisory has been issued for them (or then have been requested to) will flash their lights to make identification easier.
Another possibility is that you saw the “ice lights” that illuminate the wings to check for icing (don’t know if a diesel 9 has those) or the pilot was checking for precip.
You even might have seen a strobe light.
Speaking of strobe lights. Are there some planes that both wing strobe lights flash in unison? I think I saw that yesterday morning.
Not likely. He said they were at the base of the wing root.
Yes. This is common. The PC12 has this style. The A320 series strobe twice, both sides at the same time. (so does the MD11 or DC10, can’t remember)
Go outside. Look up!
I know what you’re talking about. The Kenmore Air Beavers do this sometimes as they fly a left downwind for water runway 18 at S60. It makes noticing them a lot easier. But it’s still easy to see them when they’re on their way down from the traffic altitude at about 600ish AGL. My house is where the red X is and is about 200 MSL. The pattern altitude is 1044 MSL.
Not to mention that some planes have the pulse feature where they flip the switch to the pulse position and leave it there till on a shorter final.
Maybe there was a temporary loss in communications and the plane was getting the attention of the tower or communicating back to the tower after they got a light signal like a steady green.
Citations have the wig/wag landing lights.