Well if you suck the modern characters through a wormhole vortex thing inside a carnival ride, then they could play in D&D.
There is precedence for that......
In this corner, ten years old and weighing in at 65 lbs soaking wet, Brandon Jaspers the barbarian, armed with a club and a goat we told him is a baby unicorn.
And in the challenging corner, weighing more than your house, and as old as reality, the immortal five-headed dragon goddess, Tiamat.
Round one. Fight! Oh wow. That was fast. Oh geeze. Wow. This was really not a good idea.