Leicester City sits atop the Premier League by five points with 13 games left in a 38-game season as it heads into a pivotal match on Sunday against perennial power Arsenal. If the previous sentence doesn't mean anything to you, imagine if the Philadelphia 76ers were the top team in today's NBA standings or the Cleveland Browns had the NFL's best record heading into Week 12.

Even those comparisons might not do justice to the performance Leicester City has produced in 2015-16. Not only did the Foxes have a 13-game winless run last season, they were only six points from being relegated to a lower level of competition. Leicester City wasn't even in the Premier League two years ago. The club earned promotion to England's top soccer league starting in the 2014-15 season for the first time in 10 years.

William Hill, an England-based bookmaker, had the Foxes as 5,000-1 long shots to win the Premier League before this season. If they hold on to claim the title, it would be the biggest upset in sports history, according to William Hill press officer Joe Crilly. (The Westgate Las Vegas SuperBook had given Leicester City 2,500-1 odds to win the Premier League. The 76ers, by comparison, had 200-1 odds to win this season's NBA title coming off an 18-64 season.)

There is no previous example of an underdog the likes of Leicester City beating odds as long as 5,000-1. There have been a few 100-1 or longer shots that either shockingly came through or fell tantalizingly short. Here's a look at 10 of those teams (unless noted, odds are from before the season or tournament):