Something which seems out of place, or not quite right for an undetermined reason. The general state of affairs resulting from such a situation. Example: I think something's wrong in the mailroom; I haven't gotten any mail since last week. There's definitely a caterpillar in the pudding down there.
CATERPILLAR IN THE PUDDING
Meaning of CATERPILLAR IN THE PUDDING in English
Slang English vocab. Английский сленговый словарь. 2012