  Despite powerful X-ray emission, some AGNs are known to either lack optical
emission lines (so-called 'optically dull' AGNs) or have lines that fall on the
star-forming branch of the BPT diagram ('misclassified' AGNs). Aperture effects
have been proposed to explain such atypical spectra, especially when based on
SDSS (3'') fibers. We use observations from VLT-MUSE with Adaptive Optics to
explore the spatially resolved optical emission line properties of 4 optically
dull and 1 misclassified X-ray AGN candidates. VLT-MUSE IFU spectra allow us to
investigate the extent to which the aperture size affects the emission line
measurements. The optically dull AGNs become detectable in deeper VLT-MUSE
spectroscopic apertures having the same size (3'') as SDSS fibers, suggesting
no AGN is truly lineless. However, in no case does the line become more
detectable as the aperture decreases, as would be expected if dilution by
strong continuum was responsible for making the lines appear weak. We also show
that the misclassified X-ray AGN retains the same position on the BPT diagram
in smaller apertures (down to 0.''5), demonstrating that its misclassification
is not the result of the dilution by HII regions. Thus, we conclude that
continuum swamping or star formation dilution, i.e., aperture effects, are not
responsible for atypical lines. Rather, the AGN lines are intrinsically weak.
