Euclid NISP spectra for example candidates from the UCD-never category, which are classified as non-ultracool dwarfs by all 400 customized classifiers. Full NISP spectra are shown in black, with flux points from more than two dither positions (NDITH > 2) highlighted in blue. The spectra of best-fit templates (red) are overlaid for candidates whose ultracool nature is confirmed by our visual inspection. The top four spectra are confirmed as contaminants based on our template fits and visual inspection, consistent with the classifiers’ predictions. The second-to-last candidate is best matched to an M6 template, while the last is matched to an L2 template. The vertical white band marks the wavelength range (1.25–1.85 μm) used for template fitting analysis.