…and then were killed by them

it was an old movie like 80s if not before. i saw it a while back. i can only remember two of the characters they brought to life, one was a purple monster thing and the other was like some sort of doctor. i remember this one scene when one of the kids were killed because one of the characters made him laugh to death. the film was a gore kind of film to. it was a terrible movie but one of those random ones youd find on ion or scifi or spike tv on an off day lol. please help me figure it out.