Rachel McAdams got a little more than she was prepared for from her co-star Channing Tatum on the set of ‘The Vow.’

The co-stars were shooting a scene for the film where Rachel’s character is caught off guard when she sees her husband, who she does not remember, naked.

What Rachel didn’t know is that Channing Tatum was packing heat, well fake prosthetic heat.

According to McAdams, Tatum had the props department make him a huge prosthetic penis to wear as a practical joke.

“Channing got the props department to make a prosthetic member,” Rachel reveals.

“Literally a fake penis. I didn’t know what to do. I thought, ‘Is is the real deal?’ It was very realistic. It was ridiculous, the scale of it.”

So now when all you ladies go to see that movie you’ll know why Rachel’s character is so shocked.

A giant fake penis… not so romantic anymore, huh?