This would be a comment but for the need for pictures.
The Friends bow was listed as a possible contender, but it's a fair bit bigger than the tiara (which I don't have to show them side-by-side).
The binoculars/robot head come in a touch smaller in the largest dimension, and the flower smaller still. The bow is 12×10.5 mm, the binoculars ...
The specific part (870) is identified in the other answer, however it is part of an assembly with its own part number:
827 Vehicle, Tractor Chassis
870's page mentions it has extra parts that it is used with, and 827 is the complete assembly (steering wheel + mechanism).
This page ...
According to the official description, these are for customizing the completed build:
This LEGO Batman toy playset includes 2 minifigures and children can customize their builds, minifigures and weapons with the included pack of 10 assorted Bat elements.
Bricklink will be a source of the data to answer this question.
At the time of this answer Bricklink has 59610 items in its part catalog. However, this list contains such categories like "Sticker Sheet" (3422 items), "Stickers Over Assembly" (250 items), "Special assembly" (38 items) you wish to exclude, since they are not really individual parts. This ...
According to BrickLink, the cheese slope, part number 54200, first appeared in a handful of sets in 2004.
In the mid-1990s, the AFOL community hung out on the Usenet newsgroup rec.toys.lego and its predecessor, alt.toys.lego. A Google Groups search of the archives of these newsgroups finds no references to the cheese slope.
At some point in the late 1990s, ...