system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] What would the effects be if someone happened to drink polyjuice potions from multiple sources at once?

So two separate variations to this question;

What would happen if someone drank a Polyjuice potion with a snippet of hair from two different sources?

Or 

What would happen if someone drank a polyjuice potion from one source; then drank a potion from a different source?
gpt
First question: The potion wouldn't even be brewed. The results would be similar to trying to create a luck potion.

Second question: You would change from the first person you turned into and then into the second one immediately after. Probability of internal damage or vomiting.