this is the boy volcano. you can tell it’s a man because the song says so and also it has no tertiary sex characteristics, it just looks like a volcano. it’s a volcano with a human face
this is the girl volcano. you know she’s a girl because she literally has a pretty human face and long human hair and a high voice. if they didn’t make sure you knew she was a woman you might have thought these anthropomorphised volcanoes were Gay
Pixar’s Umbrella Heteros Short 2: This Time Its Volcanos
Or, you know, these two characters could be based off of Israel Kamakawiwo’ole (IZ) and his wife, as IZ’s cover of Over The Rainbow was a huge inspiration for the song.
So there’s the slightest chance that the look of these two volcanoes might be fucking based off these two.
That’s just my take on it.