Researchers have prepared crystals of mixed-noble-gas compounds containing krypton and xenon (Angew. Chem., Int. Ed. 2021, DOI: 10.1002/anie.202102205). Their work broadens krypton’s limited chemical repertoire and deepens chemists’ understanding of the reactivity of the noble gas elements. Gary J. Schrobilgen and coworkers at McMaster University synthesized and characterized compounds containing Kr in the +2 oxidation state and Xe in the +2 and +4 states. The report of Kr(II)Xe(II) and Kr(II)Xe(IV) compounds comes on the heels of another study from the same group reporting the first mixed-noble-gas compounds. The earlier study also reports on Kr-Xe compounds, but in that case the elements were in the +2 and +6 oxidation states, respectively (Angew. Chem., Int. Ed. 2020, DOI: 10.1002/anie.202014682). In both studies, the McMaster team used low-temperature techniques to control the reaction between xenon-fluoride compounds and KrF2, and analyzed the crystalline products with X-ray diffraction, Raman spectroscopy, and quantum calculations. Nearly 60 years after krypton and xenon showed that they are not totally inert, these elements continue hinting that they may have other chemical tricks up their sleeves.