English only :)

[Magnum]

I don't know if it is even gramatically correct to say "I will dress something special." It certainly does not sound right but not for the lack of "up," but rather just for the lack of something in there - does not sound right. You can say "I will wear something special for dinner," though. I will dress IN something special for dinner would also probably sound good. But I don't know enough grammatical rules to really tell you why one does not sound right and the other does. I think I will end up compiling a list to ask my step-grandmother and will get back to you.