my new style is to wear a vintage tee over a short-sleeved cotton/oxford dress shirt w/button down collar. if you un-do the button down, and pull the collar up over the tee crew neck, it looks really rad that way. [looks best with black shirts, or blue/white gingham checks imo]
i also see some women in nyc wearing a short sleeve tee over a long -sleeve oxford- [tuleh showed this look]...not sure how i think that looks.
also if you wear a vintage tee over a lacoste or fred perry polo, again pulling the collar up over the tee crew neck, its rad. some girls actually pop the polo colar up above the tee but to me thats a bit 'trying to hard'... unless that for you.
mickey mouse is cool.