Show students these FB profiles and ask them to come up with reasons why they would accept these people as friends and why not. They might have various reasons for either of the decisions but in the end, it should be pointed out to them that they don’t know any of them personally, which should be reason enough not to accept them.
If you see they don’t know enough about internet safety, you might want to show them this video (3 min) and discuss it. With some groups, this can open a good discussion on Internet safety, if you personally need more information on this here and here are good articles you can draw from.
Ask students about their personal experiences with weird FB friends. According to some articles, these are very common, so at least some of them should have experiences.
All the examples were produced easily on this site. If you have access to computers, have your students create some weird profiles and add background stories like in the song to them. If access to enough computers is not possible, let students imagine “real” stories behind the 3 people from example profiles. Share 🙂