Desugaring, a key form of program manipulation, is a vital tool in the practical study of programming languages. Its use enables pragmatic solutions to the messy problems of dealing with real languages, but it also introduces problems that need addressing. By listing some of these challenges, this paper and talk aim to serve as a call to arms to the community to give the topic more attention. Categories and Subject Descriptors D.3.4 [Programming Languages]: Processors Keywords Desugaring; Resugaring; Semantics; Optimization The Need for Desugaring Concise core languages have a venerable place in the study of programming languages. By providing a means to reduce languages to an essence, they help us focus on important details and eschew ones irrelevant to the purpose of study. Furthermore, the difficulty of reducing some features may point to places where the language suffers from design flaws. The use of core languages is not only of theoretical value. Practical systems also benefi...