Wow, never imagined that this would be the thread for my first post...
(warning: I did link to TV Tropes, which may be a bit of a faux pas, but the only danger there is to your productivity)
I don't particularly mind the idea of "bunny slippers" - among other things they're a shout out to "No One Lives Forever", one of the greatest FPS of all time - but yeah, I could do without them.
The games that the Elemental franchise hearkens back to - MoM, HoMM, Civ, and to a lesser extent MOO/MOO2, all had their whimsical side - but Elemental seems to be staking out darker and edgier territory, and as such I can see where people are coming from when they see joke items as immersion-breaking.
It won't affect my decision whether or not to get the DLC, since as has been noted it's trivial to mod them away. In fact, there might be a place for them along with a bunch of others in a "comic relief" DLC, for when the grim piled on grim gets to be too much.