The achievement is to have all Magnus (cards) in your collection. Some cards evolve over time, like fresh green bananas that deal damage becoming regular bananas that heal and later spotty bananas that deal damage again. The shampoo card is one that, in its description, says you should try using it for two weeks. And they mean that literally. If you have that card for 336 hours, it transforms into a card called 'Splendid Hair'. It's not even a useful card, it just also unlocks the last few tracks in the music collection for some reason. It's legendary in how stupid it is.

And yes, there are 100% speedruns of the game that take slightly over two weeks!

Caligula was okay. I enjoyed the plot of the first one more, but the sequel was a lot easier to complete all sidequests in. For the record, the first game had over 500 NPCs each with a quest and most of them were roaming around certain areas, whereas the sequel has far less and you can easily look up where they are.