Former TOWIE star Mark was signing copies of his new calendar in Clintons at Bluewater shopping centre in Kent when he was introduced to the girls.
The greetings card brand recently joined forces with the charity Rays Of Sunshine, which grants wishes for seriously and terminally ill children in the UK.
Katie Wigley, 14, and eight-year-old Amber Howe are both supported by the charity and jumped at the chance to meet Mark.
Speaking at the event, Mark said: "It's an honour to have been invited by Rays of Sunshine to meet some of their wish families.
"The work that the charity does is just incredible. It's great that Clintons is supporting them and I'm glad to be able to help in whatever way I can."
Clintons hopes to raise £365,000 for the charity over the course of a year.