Comparison of the Hα FWHM and He II/Hα ratio of the 2021 flare with those of TDEs (Charalampopoulos et al. 2022) and quasars. For the 2021 flare, we show the values assuming that the flare’s continuum is a third-order polynomial, and the values are located in the TDE region in this figure. If the results by assuming other continuum model are adopted, the values will still be in this region. We present the range of Hα FWHMs of 99.87% of SDSS DR7 quasars from Shen et al. (2011) and the averaged He II/Hα ratio of SDSS early data release quasars from Vanden Berk et al. (2001).