The knuffel in question (the Summer 2013 type):
http://kofk.de/knuffel.php?i=12B8B2F0
I was feeding/playing with it, and got the "level up" message, so I clicked on the knuffel and opened up its page to choose what element to level up. However, after clicking on the element of my choice, the page refreshes and tells me my knuffel has leveled up (again) and prompts me to pick an element to raise (again). I have confirmed that the knuffel's level and its elemental digging level indeed increased, but it still keeps giving me the "level up" message... >_>;;;
I've had other knuffel level up at the same time as this one but didn't have the same problem with them.
...Okay, looking at the exp, it seems it has a lot more exp than the max exp needed to level up, so I'm guessing the knuffel got exp from my digging excursion after I fed/played with them, but I doubt it would get more than 1000 exp in that run, so... I'm not sure what happened there. o_O (Note: I haven't used the daycare and I don't have any "functional" furniture.)
tl;dr - For unknown reasons, my Summer 2013 knuffel suddenly got a huge jump in exp that made it get over 10 level-ups in one day.
P.S. - If you feel the need to reset my knuffel's level to be fair to other users or something, I think it was level 19 before this started.
Edit: Sorry, just realized there was another thread bumped up literally 1-2 days ago that's about a similar experience... orz I guess I was skimming the titles for the wrong keywords ("Summer 2013 Knuffel") and missed it. Also, is there a search function in the forums? I couldn't find it. D:
Edit 2: It did it again! This time it went from level 36 to 45... O_O