These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
As Fun are a supergroup, there's also resentment from some fans of The Format, Steel Train and Anathallo for the band simply existing. In the case of The Format, its because the supposed "hiatus" the band took in 2008 quickly became a full split once Aim and Ignite appeared. As for Steel Train, the band's split in 2013 may have been aided by Jack Antanoff focusing most of his attention on Fun. Other fans of the three bands are simply happy that musicians whose work they enjoy are finally gaining recognition for their talent.
Fridge Brilliance: As "Stars" goes on, the autotune on Nate Ruess's voice gets heavier and heavier (starting out nonexistent, then rather subtle, then obvious, progressing all the way to a bizarre, auto-harmonizing vocoder that makes him sound inhuman), fitting the song's lyrics about how hollow and soulless fame can turn out to be.
Fridge Horror: In "We Are Young"; it talks about a scar and the lead singer having given it to the woman months ago.
Likewise the Auto-Tune and Vocoder solos at the ending and during the climax of "Stars," though it's more just Narm when he starts yelling hysterically through a harmonizing effect around five minutes in.
Ruess has said he now regrets writing a song titled "We Are Young," as it's already starting to look silly when the clearly not young anymore band performs it.