I like #1 and welcome to GrassCity @Fernandog here's another one: weed IS the alien life form and its taking over the planet btw, can I star/co-star in your movie?
#6 But they have to have weed sniffing dogs that they use to find stashes in various houses/buildings as they travel. Searching for the elusive radiation-proof strain that is rumored to be hidden at Area 420.