His aging proccess
I don't know if I'm the only one to notice but it's just me or he looked a lot more older than he was on The O.C, and now he looks younger than he actually is?
http://tvmegasite.net/images/primetime/oc/2003review/donnie.JPG
2003, at the age of 21;
http://s3.favim.com/orig/42/hot-paul-wesley-stefan-salvatore-the-vampire-diaries-Favim.com-353654.jpg
2012, at the age of 29