Sia reads "Granny Mobile", a story about a grouchy granny at a garage sale.

Bluey and Bingo are playing Grannies at Doreen's garage sale. Muffin wants to play too and decides to be a Grouchy Granny.

She is making Dad push her on Doreen's old mobility scooter
that's for sale until a real Grouchy Granny arrives! The real
Grouchy Granny successfully lowballs the timid Doreen for the
mobility scooter, but Muffin refuses to get off until she pays
more!

Muffin proves to be a tough negotiator, closing the sale
for eleven hundred dollars – and even some lollies! As a
reward, she gets one of Doreen's tea towels and uses it to
become a super-granny instead of a grouchy one!