I second Character Connection in Epcot. Also, sometimes in the WS of Epcot there are characters tucked away in the back areas. If you are lucky, then you might find some with minimal wait. No wait is almost out of the question. Sometimes at the entrance of AK mid-day you'll find characters with minimal waits - but not Mickey.
MK is probably the park with the longest lines. Late at night, just before park close, a number of characters come out in the area in front of the castle, and then a few more on the other end of Main St. The lines are NOT exceptionally short, but at least at that point, you'll have done everything else, so you can more comfortably devote the rest of your time to seeing characters. (the timing borders on park closing anyhow)
Sometimes you can find oddballl characters with minimal waits - like the Mad Hatter near the teacups. Last year, he had no line and he was actually going up to people and being silly to get their smile. It was one of the best characters that I've actually seen ACTING like the character in a LONG time.
It reminded me of a picture my parents took of me with Minnie when I was very little. She walked up right behind me, and they took a picture just as I turned around and caught site of her. She hugged me.
Nowadays, most of the characters just stand, sign, and pose - without actually getting to express any of their character's personality any more. Even at the character meals. At 1900 Park Fare, the characters were so eager to move on to the next table it was almost pathetic.