Sneaking adult humour into shows or books aimed at kids is certainly not a new thing -- but it's not often you get a scene quite as eyebrow-raising as the one below.

On Sunday, Ed Brody tweeted the following images from a Biff, Chip and Kipperbook.

Tweet may have been deleted

Okay, let's go in for a closer look.

Nothing too unusual in that first one, right? Just three friends having a chat in the park.

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But then, when we move on to the next scene...

Yep: the implications in that one seem pretty unambiguous.

Tweet may have been deleted

It turns out this isn't the only adult reference that's been snuck into Biff, Chip and Kipperbooks, either.

Tweet may have been deleted

(In case you missed it, take another look at the letters on the building blocks.)