Boo from Budapest!

Angelina Jolie and Brad Pitt's kids definitely got into the Halloween spirit over the weekend in Hungary, where their mom, 35, is currently shooting her directorial debut.

Brothers Maddox, 9, and Pax, nearly 7, got crafty at school (Lycee Francais de Budapest), carving jack-o-lanterns with their classmates on Friday.

And, for their costumes, the famous tykes didn't go for the store-bought variety. Instead, an insider tells, "the kids sketched out the types of costumes they liked" and worked with their nannies to make DIY getups for the big day.

On Sunday, the Jolie-Pitt gang had a "a little dress-up party" at their lavish rented home. Pax dressed as a "mad scientist in glasses and a cute outfit," and trick-or-treated at the nearby home of a girl from his class, the insider tells Us.

Meanwhile, Zahara, 5, was "a spring fairy. She looked so beautiful, with flowers in her hair. She is such a girly-girl!"

Maddox wore an all-black chimney-sweeper-like outfit. "He is obsessed with black colors [and] loves the brush they carry," explains the insider.

Where was little sister Shiloh, 4?  Sadly down with a cold, the blonde, blue-eyed girl had to sit out the festivities. (Twins Vivienne and Knox, 2, didn't participate either.)

The kids weren't able to join their classmates for a special Halloween trick-or-treat walk through the city -- but they had candy waiting for them at school on Monday, the source adds.