Sims 2 & Sims 3 Wedding Question!!?

On both the Sims 2 and Sims 3, how do you get the person who you are going to marry to get dressed in their wedding attire? Like if I am playing a male sim, how do I get his fiance to change into her wedding dress on Sims 2? On Sims 3? Or if I am playing a female sim, how do I get her fiance to change into his tux on Sims 2? On Sims 3? Thanks!!