This is not the first time Jimmy Fallon has pretended to be Neil Young (that was when he covered “Pants on the Ground”), but it’s the best time.  With a little help from David Crosby, Stephen Stills and Graham Nash, Fallon staged a sort of CSNY “reunion” on the Tonight Show.  The quartet covered Iggy Azalea’s “Fancy,” and it’s amusing to watch a trio of 70-year-olds sing “Trash the hotel/Let’s get drunk on the mini bar.”  They finish the song off by segueing into “Suite: Judy Blue Eyes,” and despite the absence of the actual Young, the rousing parody brings listeners back to the day when folk was king.