The phrase used to define a lady's anus when doing anal intercourse when she shat liquid poo while the man kept thrusting into it, thus forming Fluffy Germs
For the trilogy of months like "No Nut November" or "Destroy Dick December" Fluffy February (FF) could be a month where participants have to choose a certain real or fictional animal (animal characters work too) and talk about them 24/7 with friends and relatives for the whole month.
example of a normal conversation with your friend
You: Hey you participating in Fluffy February?
Your Friend: Yeah man.
You: What animal are you gonna cho- oh wait let me guess-
You and Your friend at the same time: Ralsei
Your friend that talks about deltarune 24/7: wait how did you kno-