We introduce students to dimethylsulfoxonium methylide (DMSY) epoxidation of aryl and nonconjugated aliphatic aldehydes and ketones without revealing that DMSY cyclopropanates enones by Michael-initiated ring closure (MIRC). Each student performs the reaction of DMSY with one of nine carbonyl compounds, including four enones, and then analyzes the [superscript 13]C NMR and IR spectra of their reaction product in comparison with spectra of their carbonyl substrate. The spectra of products from aryl and nonconjugated aldehydes and ketones show the expected absence of a carbonyl peak and the addition of two upfield [superscript 13]C peaks (indicating carbonyl epoxidation), whereas spectra of products from enones unexpectedly (to the student) display a carbonyl peak, no alkene [superscript 13]C peaks, and three (instead of two) additional upfield [superscript 13]C peaks. Identification of the latter products as cyclopropyl ketones leads to a discussion of conjugate addition and MIRC, and it stresses the avoidance of making false assumptions regarding the outcome of chemical reactions. (Contains 4 notes, 1 table, 1 scheme and 2 figures.)