No more improvised than anything else, but they have "improv" in the name. That counts for something.IMPROV EVERYWHERE
2.1M subscribers Post about once a month [link]New York: Mass PG stunts. Also known for annual No Pants Subway Ride.
IMPROV IN TORONTO 23K subscribers Post a couple of times a year [link]Toronto: Although you probably could have guessed that it's from Toronto from their name.
FREAKY THE SCARY SNOWMAN
339K subscribers Posts a couple of times a month [link]USA: Quite repetitive, but if it ain't broke
SCARE TACTICS 69K subscribers Hasn't posted in over a year [link]Location Unknown: Defunct but was a TV show hosted by Tracy Morgan.
PRANKSIST PRODUCTIONS 73K subscribers Posts about once a week [link]Location Unknown: Elevator scares.
FRIDAY NIGHT CRANKS
307K subscribers Posts weekly [link]USA: Prankin' since 2007
OWNAGE PRANKS 1M subscribers Posts every week [link]Location Unknown: Plays stereotypical characters
JIMMY KIMMEL LIVE
1.6M subscribers Posts pranks a couple of times a week [link]Los Angeles: Street segments and viewer participation stunts.