[pessimizer]

I don't know about the app store, but a screenshot with a satirical comment superimposed is easy fair use.

[croes]

Not all countries have something like fair use. Could be a problem in the EU.

[lrem]

Only if the comment is about the screenshot itself though. https://youtu.be/1Jwo5qc78QU has some sad explanation.

[vletal]

I was thinking along the lines of not being OK to scrape YouTube rather then breaking copyright or intellectual property.

[lrem]

Oh sure, YouTube forbids that. Once there's enough traffic to care, it'll get cut off. But YouTube is somewhat unlikely to try to sue one's socks off for breaking the ToS. Copyright owners though...