Lighting a sparkler stuck into a citrus fruit - GIF

[odd one]

If video orange ignited, and not Mr. odd one, is likely due to freshness, and thickness of the rind. The combustion is in the rind, not inside.
Thin skinned citrus has very little citric oil.

Thanks, That makes since. I had actually tried to demonstrate that to him by squeezing the rind into a flame, but did not seem to be able to get anything out of it. Maybe a redo is in order with a fresher orange and hold off on the thermite.