What would happen if....?

dogs would no longer go barking up the wrong tree.

the sun will rise at night and the moon will light of day

Who says they didn't use to? If they switched sometime before we began to care about it, we wouldn't know, now, would we? Maybe there was a genetic advantage to switching - maybe to enhance the typical dog-chases-cat sort of business.

I would be singing cats and dogs.

Then I would be a lonely man in the world

if they always had then nothing. If it started tomorrow then everyone would freak out.

that would mean that cats and dogs had sex and we would have a bunch of dats and cogs running around

If that was the case, you would be asking what happen if cats meowed and dogs barked?

Then Michael Vick would be in jail for cat fights.

I would laugh my asss off