It's 25 years since Wally appeared on the pages of children's book, leading to a generation of kids with strained eyesight and a Pavlovian reaction to anyone wearing a red-and-white striped hat.
In honour of this literary anniversary, West End Lane Books has organised a treat for Wally spotters young and old this weekend.
If you spot Wally in West Hampstead on Saturday afternoon then take a pic of him and tweet it (@WELBooks) or mail it (email@example.com) to the bookshop. The shop has Where's Wally goodie bags crammed with stuff for kids, which will go to the best pictures (be warned, I may be involved in judging these!).
Bit old for a goodie bag, but still want some Where's Wally action? West End Lane books is also offering a £25 book voucher for the best adult entry.