Creatures Caves

@IndigoBeam: Wait, from the top-left corner you say? You know what could happen? Maybe the lemons are not spawned in properly. That would cause them to stay at coordinates 0/0. In DS, 0/0 is on the title/main menu screen, which still exists as empty space in playable worlds, for some reason. In C3, 0/0 is in the faaaaarrr top left of the Norn Terrarium if I am not mistaken.
Anyway, eventually something would happen to the lemons (e.g. rotting), and they update their position. Except, they realize that they are stuck in a wall and find the nearest "safe" position to respawn at.
Who knows what causes the lemons to do it in the first place, though. Do your creatures crowd around the DS lemon machine sometimes? Maybe a bunch of them rapidly spam it and cause the glitch that way.

And besides, is it really such a bad thing? Lemons are nutritious, and norns don't seem to taste the sour. You know what they say, when life gives you lemons...

@gwurfel: Actually, you can spawn in lemons at will! Try Ctrl + Shift + E in the game. But wait, there's more! Follow this link for over 2 dozen key combinations of varying utility!