Happy Christmas
From Tardis Wiki, the free Doctor Who reference
"Happy Christmas was a greeting traditionally used during the Christmas season, alternative to "Merry Christmas" and "Season's greetings".
Within the TARDIS, the First Doctor wished a "Happy Christmas" to Steven Taylor, Sara Kingdom and "all of you at home". (TV: "The Feast of Steven")
Queen Elizabeth II wished the Tenth Doctor "Happy Christmas" as he piloted the spaceship Titanic out of the way of Buckingham Palace. (TV: Voyage of the Damned)
Sarah wished "Happy Christmas" to Tommo. (TV: The End of Time)
On Darillium, the Twelfth Doctor wished "Happy Christmas" to River Song. (TV: The Husbands of River Song)