once a score I presume.

Annually.

Oh wait we're using old terms! So, once in a blue moon.

I didn't know how long a fortnight was, so I googled it. I thought maybe it was 2 or 3 days, but 14 days? You have to cross the line somewhere...

But then again they like the smell of poop, so they might like the smell of Op's dirty parents

The dog is probably just fine. He likes to bury his nose in someone's crotch and eats anything that falls on the floor anyway so he's happy.

But it was the friends he lied to.. And I would think he tried to tell his parents atleast once..

You could stock up on some baby wipes for them to freshen up between baths!

BUt then they'll try to save on that to..

Now that is Howiedoit.

(A fortnight is two weeks, not two days; it's from an old Middle English contraction of "fourteen nights.")

Once a week then at least.

Or just draw a bath of water before they get home and inform them if they don't use it they'll be wasting the water

Yep. I'm pretty sure that the OP addressed those questions in their post.

I am pretty sure that op's friends didn't expect the parents to smell that horrible.