D&D to D20M Cross-over

I am currently running a D&D campaign and it is almos to the point where my PCs are about to finish the big campaign finale that I have had planned for sometime. I wanted to throw a little twist into it an possibly have them be warped into a world unlike their own. I world where people travel in flying tin cans. A world call d20 modern.

Has anyone ever thought of doing this? I don't know if it would be a good idea, but I thought it would be pretty ineresting. I just wanted to knoe everyone's general thoughts (or not so general thoughts). I just want them to meet the rabid bunny of death... pictured below

I was gonna run that in reverse. Dump modern PC's into the forgotten realms and see how they deal with it. Upon their return to the real world they would be in UA.