The episode picked up 10 years after the previous instalment of the comedy series, allowing viewers to catch up on the world of titular couple Gavin and Stacey (played by Matthew Horne and Joanna Page) as well as Smithy and Nessa (James Corden and Ruth Jones).
The duo then made clandestine calls to the BBC's director of content Charlotte Moore, who was thrilled to hear that they were working together again.
Ruth told The Sun that while the Christmas special is being shown in a "different climate" to the original series which wrapped in 2010, she said the moment is not going to be "intentionally hurtful".
In recent years, The Queen's annual broadcast has become the most-watched TV show, based on the overnight figures which do not include viewers who watch Christmas specials on catch-up services during the rest of the festive period.
It ended on a cliffhanger, with a marriage proposal involving two major characters left unanswered.
To which Rob fired back: "I do want to know".
The Late Late Show star returned to the sitcom he created and starred in with Ruth Jones after a 10-year break to try to pen a long-awaited comeback, but said the episode had nearly remained a failure never to be mentioned outside of their writing room - until it was saved by one scene. "These are all questions that we ponder".
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At the end of the special, fans saw Nessa propose to Smithy outside Stacey's family home.
However, she did confess it was even a "challenge" to get the festive special filmed, adding: "It's a shame we didn't have more time when we were writing so we could have written more, then have it all ready to go".
Even Larry Lamb, who plays Gavin's hunky dad Mick Shipman, has urged the public to "keep up the pressure" when it comes to convincing Ruth and James to co-write a fourth season.
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Ruth Jones also defended the word "f****t" being used in the special where the characters sang The Pogues' popular Christmas song, with the co-creator saying they were remaining true to the characters by leaving the word uncensored.
The well-received show means things are looking up for Gavin and Stacey superfans because Ruth has since admitted she wouldn't rule out another chapter of the Barry/Billericay saga.
'Characters in Gavin & Stacey are kind and big-hearted, I believe.