Title text:
They're up there with coral islands, lightning, and caterpillars turning into butterflies.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3135/
... some metal band (Dethklok?) recording their song/filming their vid/having the concert on such a moon - the guitar solo intensifies as the band is lifted upwards by a soaring mountain, epicly, with lava flows.