Scratch

Scratch is a block-based programming language and the site targeted primarily at children to help learn code easily rather than HTML5's, members have the ability to share their own projects and get feedback. Projects can be uploaded directly from the development environment to the Scratch website and any member of the community can download the full source code to study or to remix into new projects.

And some projects disguises as a kid-friendly to scare children by adding a screamer at the end. and some screamers do have a warning.

Link

 * List of All Screamers Made With on Scratch