Do this early
High on Life has a ton of references and gross-out humor abound, but this one arguably takes the cake. Here’s where to find, uh, “Stan’s alien product,” which in turn leads to the missable “Carried Stan’s Load to Completion” achievement.
Following the first two bosses, head down this path in Blim City and talk to the NPC
Like several other elements of the game (including the jetpack), triggering this side quest of sorts is done after finishing off Krugis and Douglas: the first two major bosses of the game. Clearing those will unlock some more content, including the start of the Carried Stan’s Load to Completion achievement line.
To kick it off, go outside of your house in Blim City (or the portal), and veer right down the covered street. In the circle at the end (capped off by a restaurant) you’ll find Stan. Talk to him and agree to everything. After that, you’ll get “Stan’s alien product,” which is a “gallon of alien” fluid: a pickup labeled as an item in your inventory. You do the math!
And That’s it! You literally just need to have the item in your inventory (which never goes away and is never used) when you beat the final boss of the game.
Make sure you do it before you finish the game
Based on our file, it seems like you only get one shot at doing this, as clearing each boss in the game subsequently locks you out of fighting them again.
Related: How to stop the fans in High on Life on Prima Games