This flight was assigned to an A320 but an A321 was substituted. The seat assignment was not replanned however, leaving the back of the cabin empty and the CG setting was not updated. After the plane failed to respond to pitch at Vr, and continued to not respond following full aft stick, the captain (PM) added TOGA thrust and the plane rotated and lifted off. On shorter runways, this could end badly.

After landing uneventfully, it was determined the the CG during the approach was out of acceptable range. Fortunately there was no go-around.

http://avherald.com/h?article=4dd9ae59&opt=0