An episode of Space Goofs for your viewing pleasure
In short, Stupid Invaders is a game that is rarely mentioned when the Dreamcast's hidden gems are discussed, but that's not entirely fair in my opinion. It looks great and plays as good as any other point and click game could hope to; and while it's not on a par with the likes of Full Throttle, Beneath A Steel Sky, Monkey Island, Discworld, Broken Sword et al it's still a great example of this genre done well.
An interesting footnote to this article is that the original Stupid Invaders website is still online and retains all of the functionality it had back when the game was contemporary. It features some great artwork and downloadable content (including a 2001 calendar, if you have any use for it) so go and have a look. Sadly, the Dreamcast links are all broken now (they only go to the European Dreamcast homepage anyway), but there's still some fun to be had reading character bios and watching tiny AVI movies.