The compounds (2′E,2′E)-2,2′-(propane-1,2-diyl­idene)bis­[1-(2-nitro­phen­yl)hy­drazine], C₁₅H₁₄N₆O₄, (I), and (2Z,3Z)-ethyl 3-[2-(2-nitro­phen­yl)hydrazinyl­idene]-2-[2-(4-nitro­phen­yl)hydrazinyl­idene]butano­ate tetrahydrofuran hemi­solvate, C₁₈H₁₈N₆O₆·0.5C₄H₈O, (II), are puzzling outliers deviating from a general synthetic route aimed at the preparation of substituted pyrazoles. Possible reasons for this outcome, which is exceptional in an otherwise firmly established synthetic procedure, are analyzed. Compound (I) is unsolvated, while compound (II) crystallizes with a tetra­hydro­furan solvent mol­ecule lying on an inversion centre. The eth­oxy­carbonyl chain of (II), in turn, appears disordered into two equally populated (50%) moieties. In both structures, a plethora of different commonly occurring weak inter­molecular inter­actions [viz. π(phen­yl)⋯π(phenyl), π(C=N)⋯π(C=N), π(phen­yl)⋯π(C=N), N-H⋯O and C-H⋯O] appear responsible for the crystal stability. Much less common are the short O(nitro)⋯O(nitro) contacts which are observed in the structure of (I), an example of unusual “electron donor-acceptor” (EDA) inter­actions.