When Abby was taken hostage by the Zentrabots at Christmas, her Mum and Dad saw Danny enter the TARDIS with the Eleventh Doctor. Later on, once the Doctor freed Abby and the other children taken by the Zentrabots, Danny and Abby were reunited with their parents. (COMIC: The Zentrabot Invasion)
The Doctor then took Danny and Abby for another trip in the TARDIS, promising their parents they'd only be away for five minutes. (COMIC: The Tomb of Shemura)