Kinematically allowed regions for afterglow variability in the Δf/f_peak vs. Δt/t_peak plane. Solid lines with arrows represent the allowed regions for density fluctuations on-axis (blue), density fluctuations off-axis (red), multiple density fluctuations off-axis (green), refreshed shocks (pink) and patchy shell (black; for details see Ioka et al. 2005; Curran et al. 2008; Bernardini et al. 2011). In this plot we show early-time (t_peak ≤ 10³ s, grey circles; Chincarini et al. 2010) and late-time (t_peak> 10³ s, grey squares; Bernardini et al. 2011) X-ray flares together with UV/optical flares detected at 1σ confidence level (magenta circles; Swenson et al. 2013). The X-ray and optical peaks observed for GRB 120326A are shown with a blue triangle and a red circle.