At the end of Cartman joins NAMBLA after Kenny dies, his mother gives birth to him again, they both comment on how the baby looks like him and even name him Kenny, his dad then says “this must be like the 50th time this has happened” followed by his mother correcting him with “52nd”.
This isn’t foreshadowing, it’s more explaining. We’ve known Kenny dies and comes back from day 2, the only thing Coon and Freinds reveals is that Kenny is actually aware of it.