VFR flying into large terminal airports

[Rugerdog]

I've always wondered - could a small aircraft such as a Cessna 152 fly into a major airport like LAX, ORD, DFW, JFK, without an IFR flight plan? If so, how would ATC accomodate a slow moving puddle-jumper amongst the heavy jets in the traffic pattern?

I was between at flight at DFW last week and noticed a 152 on the ramp, and it got me to wondering how something like this works.

Thanks!