There's a nerd-famous one involving Penny Arcade using (IIRC) Strawberry Shortcake to parody the style of American McGee's Alice. I think PA ended up caving because it was too hard to defend the use of a character from one owner to parody something about another property entirely. The strip was definitely intended as parody, but including elements from something that wasn't the subject of the parody made it much harder to defend under that exception.

Maybe. Both cases you mention are songs, not video games. From a modern perspective you would think the laws about intellectual property for video games would be the same as for film and music. I think the long run that will be true. But some of the early precedent has treated video games more like "toys" with less speech protection.

If you are really doing this check with a lawyer who works in the area (admittedly few).