Well, the answer is probably Weetabix. My default breakfast is two Weetabix plus some other cereal (currently Special K "Oats & Honey", which seems to think it's eaten entirely by women who want to lose weight, not men who know that oats are good for reducing cholestorol), so I've had a portion of Weetabix almost every day for 40 or more years. Even when I go abroad I usually have it if it's available, although sometimes the local variety isn't quite the same (those Australian ones look like they're made of recycled carrier bags dyed brown).
Anyway, because of my extensive exposure to Weetabix, I notice when there are Things Wrong with it. So it is that I say good riddance to the packet of 24 that I've just completed because, well, see for yourself:
The one in the middle is from a regular pack. The ones at the outside are from the one I just finished. They're a different shade of brown.
Isn't it great that Weetabix packs are in landscape format and every other cereal is in portrait format, so they screw up supermarket shelf arrangements?