Here's what I found on tumblr:
"If you’re wondering what all this thread and twine item talk is, it’s part of FR’s April Fools day celebration!
Here’s what you need to know:
•You already have a Marva’s item in your hoard. Check the “Other” tab. It is not acquired through gathering or anything else; it’s automatically given to you.
•There are 5 different colours/types. They are: Marva’s Astonishing Cord (black), Marva’s Wondrous Thread (pink/blue/yellow), Marva’s Marvelous Twine (white/blue), Marva’s Glorious Yarn (green/purple), Marva’s Stupendous Fiber (purple/yellow).
•It appears each person receives a randomised colour in their hoard.
•You can open the item as many times as you want. It will change colour each time you open it.
•Following last year’s April Fools item, the function of the item should change on April 2. At that point the item will likely become “fixed” or functionally a regular chest-type item, and (if the pattern from last year persists) some kind of other item should pop out of Marva’s thread. (Last year it was bunny familiars. The type of familiar you got depended on which state/colour you left your Marva’s item in. I suspect the pattern will hold for this year as well.)"
Post over here
- - - Post Merge - - -
And
Over here is the cycle of the items.