I’ve just realised what’s going on here.
Thought the visit was a pre-arranged thing to make sure that Ant was OK and cool with the babysitting duties.
But it seems like it’s pals calling round to visit these parent people out of the blue, but barging in anyway, despite the parent people being out. Which is weirdly imposing wrong 'un behaviour, and what to call it is the least weird thing going on.