Stan Lee aside, just about every comic cameo is weird as hell. Seeing faces you recognise outside of the realm of comics suddenly in one is jarring, in the same way seeing a teacher or boss anywhere other than a weekday is weird.
This is doubly true when said cameo turns out to be particularly surreal - be it through a strange plot, them being characterised weirdly, or even just them being totally at odds with the comic they are starring in. The intrigue an unusual cameo can pull to a comic often means writers are strong-armed into putting folks into a story that aren't necessarily appropriate - a habit especially bad in the older ages of comics, but is still fairly present now.
That said, even the most peculiar of cameos manages to be interesting, if only to see how people like Stalin and Penn and Teller fit into the world of superheroes (which, admittedly, isn't well).
Between the leaders of countries, TV stars and dead icons, these cameos prove that just because you can put someone in a comic, doesn't mean you should.