Ben Affleck and Jennifer Garner

Ben Affleck and Jennifer Garner

Ben Affleck and Jennifer Garner reportedly crashed a child's birthday party with their son.

The 41-year-old actor, who is currently filming 'Batman v. Superman: Dawn of Justice' in Detroit, stopped by a local children's centre with his wife and their youngest child, Samuel, two, on Sunday (13.07.14), unaware that it had been booked out for another child's private Superman-themed bash.

But the host was thrilled to see the Oscar-winning director and the 'Butter' actress, and asked them to join in on the festivities.

Garrett Dixon of the facility, Detroit Kid Centre, told the Detroit Free Press: "I spoke with Ben for 10 or 15 minutes and he was very pleased with the facility. He was very interested in getting a Detroit Kid City out in L.A.

"He said they had a blast and will definitely be in contact with us."

Jennifer, 42, recently admitted she and Ben, with whom she also has daughters, Violet, eight, and Seraphina, five, try to be a normal couple because they are determined to set a positive example to their kids.

She said: "We want to be a healthy couple and to make time for us as well as for the children and we find ways to do that."