“Last week ago” is my favourite Alex-ism right now. (There are so many good ones, like “have to try and avoid that,” and “we’re alllll cats.”) But this one combines his growing sense of time with a subtly mutated idiom in an unutterably cute three-word package.
“So, Alex, when did you stay overnight at Grandma and Granda’s house?”
“Last week ago I did that.”