Ah, I think it's funny that others are finally starting to repeat what I've been saying. That being, I'm staying at Universal and want to visit the MK and Epcot in 1 day, can it be done?
Not ragging on the OP, but we've been seeing this a lot lately. Disney people always want to try to dip their toe in the water, but only spend ONE day to visit both parks. It can be done, but only if you arrive the parking garage at 8am.
What we usually find, is people who arrive late at 11am, they run into large crowds, don't feel the magic, and go home unhappy. The fact they you're staying at Disney already puts a negative on things. To get the full effect, you have to stay onsite at Universal. We've tried to be nice and explain it, but it's very hard to do without screaming what Disney people are doing is just wrong.
Here they'll stay at Disney for a week taking their time. But to try Universal, they will only take one precious day away from Disney, and cram two parks into one day. It doesn't work. Any little thing that goes wrong, from the walk to the gate, to the way the characters interact, to someone bumping you, to anything, will make your view jaded.