Cheek kissing

Cheek kissing was a friendly gesture. Charles Dickens described it as "modern" in 19th century culture when Rose Tyler kissed him on the cheek. (TV: The Unquiet Dead) It was viewed as unusual in the 21st century. The Eleventh Doctor used it when meeting Craig Owens and Sophie. (TV: The Lodger)

Nyssa kissed the Fifth Doctor on the cheek when she chose to remain on Terminus, (TV: Terminus) with the Eighth Doctor later returning the favour. (AUDIO: A Heart on Both Sides)

After believing that the might have saved Gallifrey at the conclusion of the Last Great Time War, Clara Oswald kissed the Eleventh Doctor on the cheek as a show of support when he regarded Gallifrey Falls No More. (TV: The Day of the Doctor)

When the Twelfth Doctor was reluctant to regenerate, the glass avatar of Bill Potts kissed him on the cheek, returning his memories of Clara Oswald to him. (TV: Twice Upon a Time)