The code can only be used once for every monster and so far, this code has no expiration date. Once the seed is planted in the garden, the player has to plant it with two other random seeds (for example: Love Berries and Star Blossom).
As of April 2014, the Radiant Roxy Rode can also be obtained via Roxy's Moshlings Collection plush toy, thus allowing the player to have multiples of the Moshling.
Buster Bumblechops, Moshling collector extraordinaire at your service!
Thanks for getting in touch. I hope you've enjoyed reading about my
hair-raising adventures in the Moshling Collector's Guide. I'll bet
you're super dooper curious about how YOU can get ahold of the
fabulous Roxy the Precious Prism, the hottest, blingiest shiniest new
Moshling on the block. Well, because you asked real nicely, I'm gonna
All you have to do is go to the Moshi Monsters sign in page
(www.moshimonsters.com/login), type in the word HOBBIDIDANCE in the
unique item code box, and sign in. Type carefully, and make sure you
spell the word right. Once you're in your monster's room, go to your
garden, and you'll find a special seed in your seed bag - The Radiant
Roxy Rose. Plant it along with any two other seeds, wait 'til it
grows, and then TAH DAH! You'll have your very own Roxy.
By the way, I'd be much obliged if you'd keep your lips zipped on
this. It's a SECRET!
I'll be seein' you 'round Monstro City... Happy Moshling huntin'