Have you ever bumped in to someone and then struggled to remember where you've seen them before? I wonder if that happens in movies, too.

Some actors seem destined to play together more than once. I don't mean that they act together in sequels; rather, they seem to play together in completely different movies. Richard Gere and Julia Roberts in Pretty Woman (1990) and in Runaway Bride (1999) are one great example; Tom Hanks and Meg Ryan in Sleepless In Seattle (1993) and You've Got Mail is another classic example; and Leonardo di Caprio and Kate Winslet are the third pair, starring in Titanic (1997) and Revolutionary Road (2008). Arguably, these actors were brought back together for their on-screen chemistry.

But they aren't the only ones…

"Haven't I seen you in the computer?"

When Joe Pantoliano and Carrie-Anne Moss appeared together in The Matrix (1999), they skipped back and forth between reality and a made-up world. Imagine their confused surprise when they bump into each other again during Memento (2000), a show in which one character struggled with reality.

"I was looking for you!"

Matt Damon and Gwyneth Paltrow and Jude Law appeared together in The Talented Mr. Ripley (1999), and then they appeared together in Contagion (2011). Twelve years after the three were caught in a lover's triangle in Europe, they were fighting a global pandemic!

"Are you looking at me?"

The movie Heat (1995) was famously advertised as the first movie that Al Pacino and Robert Deniro star in together. This is only partially true. They were both in The Godfather Part 2 (1974)... Just never in the same scene.

"Forget the bus, let's meet at the lake house"

In the hit movie Speed (1994), Keanu Reeves and Sandra Bullock faced off against an evil villain bent on blowing up a bus if it slows down. Years later, Keanu Reeves and Sandra Bullock fell in love (sort of) at The Lake House (2006).

"Thieves or sweethearts"

Julia Roberts and Catherine Zeta-Jones played together in the romantic comedy America's Sweethearts (2001). Later, they met again as the love interests to thieves in Ocean's Twelve (2004).

"Is that you, dad?"

Possibly the strangest case of playing together is the father-son acting team of Martin Sheen and Charlie Sheen. In the movie Wall Street (1987), Martin Sheen play's Charlie's father – a role that would have been easy to portray. But then in the little-known but excellent movie Cadence (1990), Martin Sheen plays a father figure (but not the father of) Charlie Sheen's character.

In spite of the number of gifted actors and actresses in Hollywood, we do see actors reappear with each other in movies. Sometimes we like the chemistry and demand it, other times it just seems to be a happy coincidence. Next time you notice two actors reappearing together, you have to wonder if they're thinking: "Have we met before?"