Like computer programs that run automatically on your computer, whether you want them to run or not, because their programmers have decided they automatically should. Any person (or program) that takes over from a mind set of self-importance, whether someone has asked them to be the center of attention or not.
Ever since Amy came in here, and took over, things haven't been going well.
Yeah, she's really quite the self-important program isn 't she?
My computer takes a long time to reboot, it has lots of self-important programs running.