Re: UFO plants. The truth may be out there...but the plant is not!
The UFO plant is the only alien plant that's base game, and (with apologies to the esteemed jpkarlsen) they are NOT on Sixam. There are only two ways to get the UFO plant that I'm aware of, and they're both very random. Both involve rocket missions.
1. If you get the Space Race card, you want to try to win the race because the UFO fruit is the prize (sometimes? always?).
2. If you get The Green Man card, the UFO fruit is a possible reward.
Further details behind a spoiler cut, in case you (or someone else) wants to be surprised and that's enough of a hint.
Spoiler
For the Space Race card, you need upgraded thrusters and to push it. For the Green Man card, lol I usually fail this one. I've seen mixed instructions on how to succeed, so perhaps it's random or tied to a skill (fishing for the swamp?). I think I succeded once with exploring the jungle and not taking a weapon, but I've also failed the jungle and someone else on google says you need to forage the swamp and take a weapon (and I KNOW I've failed the swamp!), so...?
Good luck!
[Edit] I just googled and someone else said they'd gotten them from the "accidental bootlegger" card. I usually get mine from the Space Race.
