THIS COMM HAS MOVED
The joke
The second image is a Ptolemaic statuette of the Egyptian deity Anpu from perhaps ~200 BCE. It is old. So is the bus. Additionally, Anubis was sometimes known as "The Dog who Swallows Millions", compared here to the poor economy of school buses. Finally, I'm not very good at understanding jokes. Hope that helps.
EARSIS
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I thought it was Anubis rather than Anubus
Vowels weren't written in Egypt until Coptic came around much later so either could be right!
But didn't poetry and such, i.e. rhyme give hints to what the vowels could have been.
I will forever approve this message. I used to end my radio show in college with that clip, "... over?!..."