25 nearly identical pairs of movies that came out around the same time

Sony, Columbia Pictures / Film District

Both "WHD" and "OHF" featured main characters saving presidents from an all-out attack on the White House. "Olympus Has Fallen" was released in March 2013 while "White House Down" received a June release date.

After the first box-office bomb of the year, Gerard Butler will return to theaters this weekend in the sequel to 2013's "Olympus has Fallen," cleverly called "London has Fallen."

You may remember "Olympus has Fallen" - a movie about a president taken hostage - for bearing a striking resemblance to Channing Tatum's movie "White House Down," which came out three months later.

Critics and fans alike were quick to point out how similar the two movies were to each other.

But this wasn't the first time two films with "twin" plots were released around the same time, and it certainly won't be the last.

So why does this happen so frequently? It's all about the competition.

Forbes contributor Mark Hughes summed it up best in a 2011 Quora post explaining that sometimes it's just coincidence. However, it could also be to piggyback off a competitor's potentially successful - or already successful - project.

Read the rest of his explanation here, and keep scrolling to see 25 "twin" films that have come out months apart in theaters over the years.