I have a suggestion: the huge numbers are not quite readable. Maybe add the scientific notation as well. Comparing 73,400,000,000,000,000,000,000 with 844,000,000,000,000,000,000,000 is tricky, especially since the numbers are not right aligned.
Adding a 73.4×10^21 vs 844×10^21 would be helpful.
IMHO it could lose some of the silly charm with scientific notation.
But having the numbers aligned for easy comparison would be great.
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To OP: I really like this! Will be guessing some with my kids who are around 10 year old. Combined weight less than an elephant.
4,200,000,000 (4.2 billion)
1,000,000 (1 million)
900,000 (900 thousand)
Of course you might have the issue of short scale vs. long scale billions but a footnote should solve that.