The British hunk reprises his role as 007 in the upcoming 23rd installment, while Harris plays special agent Eve.
The actress spent weeks learning to fire guns before filming began, but she admits the shoot was less than perfect at times - and Craig often stepped up to help shoulder the responsibility.
She tells InStyle magazine, "It was all quite nerve-wracking, but he was very reassuring. It was great to have someone be like, 'We're just going to do this together, it's going to be OK, and if you don't get it right, we'll do it again.'
"Sometimes I'd mess up and he'd say things like, 'No, it was me' and take the blame."