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/
Gasp! I'm telling my mamma you said that about her!!
(because it's gonna make her giggle like an idiot, too, like it did to me!)