It’s a pun in Portuguese indeed. “Eis que” = a generic old fashioned way to start a phrase, like “behold”. “Behold what?”. “Eis que leto” sounds like skeleton. kkkkk is laughing sound and é muita comédia agrees that’s a good joke.
This community is for puns in Portuguese. I particularly like them. Be welcome in case you want to practice your old lessons here. I guess it’s a challenge