I pulled this Haro bike outta the trash 2 days ago
put a tire on it and my grandson was already riding it
noticed the crank is on the left side
looked at some pictures of other ones
noticed the crank sometime on the left, sometime on the right
anyone can shed some light on this?

I figured it out
it is for left handed trick riders
who lead and are stronger on the left

if is for riders who prefer to grind ledges and handrails on their right side, so they don't bash up the chain.

What you refer to is actually the chain guard. 8)

left handed mechanics sometimes do this using left handed wrenches.

tjkoko- there is a chain guard on that bike, but the OP is asking about the fact that the entire drivetrain is in fact on the left side of the bike. for this to work, the crankset and the rear hub are designed to accommodate a LHD (left hand drive) system. the sprocket locator bolt is on the left crank arm, or on both the left and right. the hub engages when the driver is spun anti-clockwise and only works on a LHD-specific hub.

I wrote a tech article for BMX riders some time ago. some of the information is a bit dated but this gets the general idea- bicycle necromancy: left-hand and right-hand drives

yea sometimes it does on the left