met zijn neus in de boter vallen

Etymology
Literally, “to fall with one's nose into (the) butter”.

Earliest attested use in 1613, in 's Klucht v.d. Molenaar, vs. 474, as "mit myn neus in 't raken" (to fall with my nose in the fat)

A couple of more vulgar variants such as "to fall with one's asshole into the butter" exist in Belgium (met zijn gat in de boter vallen) as well as in Friesland (mei 't gat yn 'e bûter (or bûterfet) falle), both typically used to denote someone who was born into wealth, or in Friesland also a woman who married her way into a rich family.

Verb

 * 1)  to be lucky, to be in luck; particularly: to arrive at a lucky or opportune moment