Is a MacGuffin *always* an object or character?

First off, I'm new here, so hi. Forgive me if this is an obvious question.

I'm working on a short screenplay for a filmmaking class, and the plot revolves around a boy visited by an alien who happens to be his father. The alien wants to bring the boy back to their home planet for a reason that doesn't really matter in the overall plot; what matters more is the interaction between the alien, the boy, and the boy's earth-father. Would the reason for the alien wanting the son to come with him be considered a MacGuffin, or something else?

I wouldn't say so. A MacGuffin is usually an object of some kind, or at least a tangible thing. There are variations for when a person fills this role; for example, by being a metaphysical embodiment of the thing being sought after, someone whose physical or spiritual qualities make them the object of everyone's conflict, or a token "important person" to be kidnapped and rescued. Tons of other variations occupy that trope's page as well; it's a big concept precisely for being so common.

edited 26th Feb '15 12:01:48 PM by Fighteer

What would you call an unimportant but motivating plot point then?

You might want to broaden your search a bit to the Plot Device trope.

But Plot Device still seems to refer to objects or characters, whereas I'm looking for something that rather describes a situation that advances the plot.

edited 26th Feb '15 12:07:16 PM by TheGuyWhoMakesThings

You might want to hop over to Trope Finder to see if you can get advice from a broader selection of tropers.

Thank you for the suggestion.

Some works do treat intangible things as tangible though like a thought could be treated as tangible and fought over the course of the plot and such.