It's a Wonderful Life was a film about Christmas.
When the Eighth Doctor told the dark-haired version of Samantha Jones about the blonde version of her who travelled with him, she thought it was a practical joke like in It's a Wonderful Life. She said her mum cried through it every time it was on television. (PROSE: Unnatural History)
The Eighth Doctor said that Christmas brought communities together, like in It's a Wonderful Life. (PROSE: Not in My Back Yard)
Peri Brown told the Fifth Doctor that she wanted a Christmas on Earth, which had, among other things, It's a Wonderful Life on TV. (PROSE: Far Away in a Manger)
Behind the scenes
The characters in Flip-Flop are named after characters and actors in It's a Wonderful Life.