Trick or Treat

Trick or Treat/Halloween is basically an American thing.
Over recent years it has made some inroads into UK but it is little known in Europe generally. If you find anywhere, it will be where there are (American) ex-pats living.
My neighbour is a hairdresser and she decorated her salon a couple of years ago with cheap tat - spider's webs, plastic skeletons and so on - but, when we asked her about it, she had absolutely no idea of the significance of it all and had never heard of 'Trick or Treat'.

Lots of locally arranged trick or treats organized in and around the waterloo area due to the high number of Americans living there. The commune of Lasne organizes something every year as well, They do a parade around Plancenoit. Police block the roads off and everything. Since my daughter isn't at the school anymore I don't know the dates. It's usually on the weekend after halloween.

It's not a thing I miss being hounded by children with menaces for sweets. It's a catholic country why would they celebrate it? Sort out your own route with friend who are willing to participate rather than hounding confused locals.

It's maybe not exactly what you're looking for, but every year in St Gilles there is what's called a witches walk from Parc Pierre Paulus. It starts with a bit of a party in the park with ghoulish music, drums, fire shows, scary costumes and for a bit of Breton/Celtic stuff (Halloween is a very Celtic thing in the minds of les belges) and then the parade makes its way to the Fantastic Art Museum, which is just beside the Horta museum on Rue Americain in Ixelles. I'm pretty sure it's sponsored by the Fantastic Art museum, and once everyone arrives there (there's usually a good one hundred or so people) they do a pretty lo-fi scary monster bit from their tiny balcony and fling out sweets to the crowds below. It's pretty cute and home-made, and as an added bonus, absolutely everyone is kitted out as ghosts, witches, monsters etc, old school style, as opposed to Spice Girls and sexy nurses, as the case might be at home. Last year before the walk they invited everyone into some beautiful vielle maison near the starting point of the walk, where there was a little exhibition of ghoulish paintings by a young Belgian artist, with free wine for the adults and hot soup for the kiddies. It was all very cultured. Halloween, Belgian style. The kids loved it. There's nothing official yet on their website, but here's the details on Facebook. https://www.facebook.com/pages/Musée-dart-fantastique/124878687571837