Get your aggressive heathen or Rascal to chase your selected individual. SLOWLY move your person ahead of the yellow-mask(s). Slowly lead them to a secluded spot, away from a busy or well traveled area. When you get them to your spot, keep your person above them and press the "M"/Map key.

This will freeze the yellow-masks in place with your villager suspended slightly above them.

You can add to your 'collection' by repeating the Pied Piper action with other yellow-masks. When you get the next group to the holding area, press the space bar, pull the villager you want to release out; everyone starts running around, grab the other villager & place him/her in the middle.

If some of the aggressives start to wander off, place your villager near them and move back and forth between the aggressives. When they are consolidated, press the M key.

It will take some practice but you can exchange your villagers. Move one away, and get the clump to gather around the villager you want to hold them. I can usually hold 5 or 6 at a time.

Sometimes another Rascal will pop up, but not often, or the yellow-masks will be released, but usually not while the game is being played. If you shut the game down, the heathens are released.

DO NOT pick up a collectible near them, or they are usually released.