In its various incarnations, the Hart Foundation was one of the most influential and longest-lasting professional wrestling stables in the World Wrestling Federation.
 

Hart Foundation 1.0: The original Hart Foundation consisted of Bret "The Hitman" Hart and Jim "The Anvil" Neidhart, with Jimmy Hart as their manager.  Bret and Neidhart entered the World Wrestling Federation in 1986 and began teaming with each other right away,   They won the WWF Tag Team Championship for the first time in early 1987, beating The British Bulldogs after evil referee Danny Davis helped them win.  They'd hold the belts until October of '87, when they were beaten by Strike Force (Rick Martel and Tito Santana).  The two would continue to team together until 1991, winning the tag belts one more time (won from Demolition at SummerSlam '90 and lost to The Nasty Boys at Wrestlemania VII).  At that time, the team was split up so that Bret could pursue a singles career.
 

Hart Foundation 2.0: When Owen Hart rejoined the WWF in late 1991 (he had a prior run with the company in 1988-89 as the Blue Blazer), he joined with Neidhart to form the "New Foundation".  The team didn't last long, as Owen got moved into the singles division soon after and Neidhart would fade into obscurity for years.
 

Hart Foundation 3.0: In preparation for an Owen vs. Bret series, Owen Hart, Bret Hart, Bruce Hart, and Keith Hart all competed together at Survivor Series '93.  After teasing a heel turn there, Owen and Bret would team together until Royal Rumble '94, when Owen finally turned to set up the feud.  The two would go on to have phenomenal matches against each other at Wrestlemania X and SummerSlam '94.
 

Hart Foundation 4.0: Bret Hart turns heel at Wrestlemania 13 and embarks on a pro-Canadian, anti-American angle shortly thereafter.  During one taping of RAW, he calls Owen and Davey Boy out to the ring, where he asks for their help in his war against Stone Cold Steve Austin and his anti-hero ways.  The three join forces and reform the Hart Foundation n a tearful reunion; Brian Pillman and Jim Neidhart would soon join them.  This was an extraordinary angle, as the Foundation would remain hated heels in the United States while being treated like heroes in Canada and elsewhere.  This is especially evident at Canadian Stampede '97, which took place in Calgary, Alberta, Canada--the Harts are given a thunderous ovation while supposed babyfaces Stone Cold Steve Austin, Goldust, the Legion of Doom, and Ken Shamrock are booed out of the building.
 

The Hart Foundation pretty much fell apart at Survivor Series '97, when Bret was turfed out of the WWF--Neidhart and Davey Boy quit in protest, and Pillman had died two months previously due to a heart condition.  No incarnation of the Foundation has been seen since.