12) Captain Underpants and the Attack of the Talking Toilets, by Dav Pilkey
13) Captain Underpants and the Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space (and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds), by Dav Pilkey
14) Captain Underpants and the Perilous Plot of Professor Poopypants, by Dav Pilkey
15) Captain Underpants and the Wrath of the Wicked Wedgie Woman, by Dav Pilkey
16) Captain Underpants and the Big, Bad Battle of the Bionic Booger Boy, Part 1: The Night of the Naughty Nostril Nuggets, by Dav Pilkey
17) Captain Underpants and the Big, Bad Battle of the Bionic Booger Boy, Part 2: The Revenge of the Ridiculous Robo-Boogers, by Dav Pilkey
18) Captain Underpants and the Preposterous Plight of the Purple Potty People, by Dav Pilkey
Young F is a big fan of this series of books, so I worked through them myself over the course of this week. It did not take me long; none of the lavishly illustrated books is even 180 large type pages in length.
Our protagonists, George and Harold, accidentally transform their school's principal, Mr Krupp, into superhero Captain Underpants. This is fortunate, as their Ohio town is a bit of a focal point for invading aliens and deranged scientists, who tend to have a fixation with toilets and/or underwear and/or body fluids. George and Harold, and Captain Underpants, save the day, though the latest books end on cliff-hangers to lead into the next story.
The books are all pretty similar but quite funny, and I can see why F likes them. I wondered whether the time-travelling portable toilet in the last two books drew some inspiration from Doctor Who? More likely that it's second-hand inspiration via Bill and Ted, I suppose. Note on the Bechdel test, though: almost no female characters apart from members of the psychotic school staff and the odd - very odd - parent.