Gavin and Stacey star Laura Aikman's involvement in the last ever episode was so top secret that even her own family had no idea she would be in it.
Fans tuning in to watch the series final on Christmas Day were gasping over their Christmas pudding when a shock twist showed James Corden's character Smithy was preparing to marry girlfriend Sonia - played by Laura, 39. The last Christmas special that aired in 2019 ended with a cliffhanger proposal where Ruth Jones's Nessa proposed to Smithy, and fans were expecting the episode to focus on their long-awaited wedding.
But instead, fans watched as Smithy marched his way through a branch of John Lewis to find his wife-to-be as they were finalising their wedding gift registry - only for Sonia to be revealed as his blushing fiancée. During the weeks that Gavin and Stacey filmed in Essex and Wales over the summer, paparazzi shots showed the familiar cast of characters moving around for scenes.
But, astonishingly, Laura's involvement as Sonia was kept a secret until the episode aired on Christmas Day - and even her own family had no idea she was going to feature in the episode. Taking to social media after the episode aired, Laura shared video footage of her family reacting in shock to see her on their TV screen.
She uploaded the content to her Instagram grid alongside a caption that stated: "I take an NDA very seriously." And she added: "The moment my family realise Sonia is ruining Christmas again..." Her family were stunned by the reveal - and one could be heard gasping: "You never told me" - with Laura replying: "We never told anyone."
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Revelling in the spotlight, the star later revealed that the cast grid even left her out so as to avoid any spoilers being leaked. She shared a photograph of the order of cast with headshots of all the actors - with a huge gap where cast member number 13 was supposed to be. She then shared a screenshot of herself in the episode and wrote: "Many apologies for my behaviour."
Fans watching the finale saw Sonia constantly belittle Smithy in the run up to their wedding - while Nessa expressed her disappointment over the fact he had rebuffed her five years earlier. But by the end of the episode, Mathew Horne's Gavin Shipman plucked up the courage to object during the wedding and saved his friend from marrying the highly strung character.
Show creators Ruth and James previously discussed emotional details about the finale during a special screening for cast and crew. Speaking at the screening, Ruth said: "I'm feeling a bit drained. It was so lovely to watch it with an audience. I hope we did you proud. It was just lovely to hear all the reactions. To hear that very initial response, it's just gorgeous." A tearful James said: "I just wanted it to feel satisfying really. What was really interesting is after the 2019 special, all people would say to us was, what does he say? They would never say who did he choose.
"I called Ruth and I was like, I wonder if we could trick everybody into thinking that for the first six or seven minutes that they're just going to watch a wedding between Nessa and Smithy. I remember so vividly having that chat with Ruth going, 'oh, I wonder if we could pull that off. I feel like we did'."
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