Leaving it as "check translation" because I'm not 100% sure about the 呑めん + めんばー portmanteau. I checked some webpages that talk about this commemorative day, but it seems all of them just use the sentence without explaining it further.
Is there a name for that gator/fox creature riding piggyback on the Sukonbu at bottom center? It also shows up as a hairclip in post #8407294, so it's not just a one-off.