Crazed fans and paparazzi will often try to sneak into star-studded events or parties, but how often do celebs show up unexpectedly at average folks' gatherings?

While it may be rare, these encounters do happen. And even though a "regular" person's wedding might seem like the last place a famous face would drop by, A-listers -- and even royals -- have proved us wrong by dropping in on strangers' nuptials.

Click through the slideshow below to see which stars crashed regular peoples' weddings, then let us know in the comments: Which celeb would you want to crash your wedding?

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  • Justin Bieber and Selena Gomez

    Teen heartthrob Justin Bieber and then-girlfriend Selena Gomez were strolling on the beach in Malibu, Calif. in July 2011 when they heard Bieber's hit song "One Less Lonely Girl" playing at a local wedding reception. According to <a href="http://www.tmz.com/2011/07/18/justin-bieber-selena-gomez-crash-malibu-wedding-video/" target="_hplink">TMZ</a>, the famous pair snuck up on some guests and then got on the mic to give the newlyweds a toast. "We just crashed it. We heard a party so we decided to just come. So let's party," Bieber said in <a href="http://www.tmz.com/2011/07/18/justin-bieber-selena-gomez-crash-malibu-wedding-video/" target="_hplink">an exclusive video</a>.

  • Meryl Streep

    When Freya and Graham McAnally <a href="http://www.dailymail.co.uk/news/article-2068926/The-Iron-Lady-Meryl-Streep-gate-crashes-Manchester-couples-wedding-dressed-Margaret-Thatcher.html" target="_hplink">got married</a> at the Manchester Town Hall in England in December 2011, they knew that cameras were nearby filming "The Iron Lady" starring Meryl Streep. But what they didn't know is that Streep would show up at their wedding. According to <em>The Daily Mail,</em> the Oscar-winning actress made an appearance at the couple's nuptials, then sent them autographed photos of herself bearing messages of congratulations. "I thought it was amazing, the last thing you expect is an A-List celebrity at your wedding," <a href="http://www.dailymail.co.uk/news/article-2068926/The-Iron-Lady-Meryl-Streep-gate-crashes-Manchester-couples-wedding-dressed-Margaret-Thatcher.html" target="_hplink">the bride said. </a>

  • Queen Elizabeth

    Believe it or not, royals crash weddings sometimes too. In <a href="http://articles.cnn.com/2012-03-25/world/world_europe_uk-queen-wedding-crasher_1_queen-elizabeth-wedding-gift-prince-philip?_s=PM:EUROPE" target="_hplink">March 2012</a>, Queen Elizabeth showed up at John and Frances Canning's Manchester, England wedding and completely shocked the couple, who had invited her but never really expected her to actually attend. "Basically it was a wedding gift for us," the bride <a href="http://articles.cnn.com/2012-03-25/world/world_europe_uk-queen-wedding-crasher_1_queen-elizabeth-wedding-gift-prince-philip?_s=PM:EUROPE" target="_hplink">told</a> CNN affiliate ITN.

  • Adrian Grenier

    In September 2008, "Entourage" actor Adrian Grenier accidentally walked into a wedding while leaving the Ritz-Carlton's spa in Marina del Rey, Calif. But according to the <em><a href="http://articles.nydailynews.com/2008-09-11/gossip/17907189_1_opens-las-vegas-t-shirt-dresses/2" target="_hplink">New York Daily News</a></em>, no one really seemed to mind. In fact, some guests were all too eager to take some snapshots with the actor.

  • John Travolta and Robin Williams

    John Travolta and Robin Williams once crashed a wedding together, but it was long before the two were big in Hollywood. <a href="http://www.usatoday.com/life/movies/news/2009-11-18-olddogs18_st_N.htm" target="_hplink">According to <em>USA Today</em></a>, the friends had stopped to get a drink near Travolta's Santa Barbara home back in 1977. After a few drinks, "We were having fun, starting to relax, when we saw there was a wedding next door," Travolta told <em>USA Today</em> <a href="http://www.usatoday.com/life/movies/news/2009-11-18-olddogs18_st_N.htm" target="_hplink">in 2009</a>. "We figured we'd crash it."

  • Conan O'Brien

    In April 2013, comedian Conan O'Brien <a href="http://www.huffingtonpost.com/2013/04/02/conan-obrien-wedding_n_3000748.html?utm_hp_ref=weddings&ir=Weddings#slide=2295456" target="_hplink">crashed an Atlanta couple's wedding</a>. A friend of the couple had been tweeting at O'Brien all day, inviting him to the wedding -- and he actually showed up! At left, O'Brien is pictured with the bride.