While an artist's corrections to his painting are often popular and can be the subject of interested speculation, the same doesn't go for body art! Changing your mind and removing your tattoo can cost you dear. The skin isn't a canvas in quite the same sense as a painter's canvas. Fortunately, solutions now exist that are less radical than some of the older methods such as skin grafts or dermabrasions which "sand down" the skin - ouch!
Laser: This can gradually erase an unwanted tattoo, but the process can be long and quite painful, depending on the size, colors and depth of the tattoo.
Retouching: Some tattooists can change and modify a tattoo. For example, a design could be added to hide a name, or letters could be added to change (Jo to John, Viv Forever into Viva Forever, etc).
Covering up with make-up: If you simply want to hide your tattoo for an occasion, there are cover-up sticks available that provide sufficient coverage. They're normally used for covering up scars but also work on body art.