Lava Lamps are functional room items. You put it in a knuffel's room and it gives the knuffel 70 EXP every hour. Go to the Living Empire to see other functional room items. They are all explained there
About the EXP glitch: The glitch is about random boost of a knuffel's EXP and leveling up like crazy, even without any activity around this knuffel (like no feeding/playing/digging/daycare/functional items/a friend feeding&playing with them etc.) It only occures for the chosen ones

Some people get them, some don't. A user can notice the glitch on multiple of their knuffel or just one. Or none, as in my case
I hope I explained everything clearly:qsml:
Also, if you want to see some newer knuffel, you can go here:
http://thekofk.wikia.com/wiki/Official_Knuffel_List the only knuff missing is the last Earth one. It's worth saving this page, since there are 2 on the web, and this one is more up to date
