Lugia dolls can be quite ah, naughty we'll say. Especially when people ignore the warning signs I put up around them. Just being near one of them induces an effect that makes one want to tug back the zipper holding its mouth shut. Once the victim touches the doll itself, their energy is drained, bringing the Lugia to life. As the victim grows weaker, the doll grows in strength. Using either brute force or by exhaling a sleeping gas over the victim, the doll swallows its target whole, content to have a permanent energy source locked away deep within.
Occasionally the Lugia might taunt its victim by rubbing its belly just hard enough for the person inside to feel it, but otherwise onlookers are unaware of what's happened.