I've said it before, and will say it again: If they're made to have a "fun sound", and not monitoring, don't call them IEMs. They are not monitors. They are in-ear headphones.
SanderSkjegstadIEM refers to the form factor/style of in ear headphone. They're not earbuds, they have larger housing, can have multiple drivers, and multiple types of drivers, and they funnel the audio through a a port into your ear. That's what IEM refers to now days, not the sound signature.
tooitchyNever called them earbuds. They're in-ear headphones or earphones. Monitoring isn't dependant on sound signature. Stage IEMs have a very different sound from studio IEMs, it's not the sound signature alone that makes them monitors, it is that they're designed for monitoring, not listening and jamming out.