Aurora Bore-alis.
Explanation: This joke is a play on words, where “Aurora Bore-alis” humorously substitutes “Bore” for “Borealis.” The Northern Lights, or Aurora Borealis, are an awe-inspiring sight, but the joke implies that someone could get bored of watching them, turning the word “Borealis” into “Bore-alis,” implying it has become boring. The humor lies in the exaggerated idea of becoming tired of something so beautiful.