I agree with
@Leadinglights. I think you have had a touch of Reactive Hypoglycaemia due to your breakfast cereal pushing your levels high. High BG levels make you sleepy, so would tie in with you having a nap ..... then your pancreas kicked in to late and too strongly and the sensation of rapidly dropping from a high BG to a lowish one makes the hypo sensation that much worse.
Of course the nature of a hypo, or a common symptom, is to make you hungry and sometimes it is difficult not to "eat the fridge" ie everything within reach. Once you get used to hypos and learn not to panic it is much easier to just take the allotted amount of fast acting carbs which is 15g (usually 3 jelly babies or 4 glucose tablets). I remember my first few hypos made me feel absolutely shocking and yes I felt like passing out, but now that I have gained confidence in treating them I don't panic and they are so much easier to cope with and often I just need 1 or 2 jelly babies to bring me back up and I can continue to work, even doing something quite physical. The panic really makes them so much worse.
I did have a bit of a giggle at you eating 5 penguins!! Real overkill but I understand why and it is very compulsive to over treat a hypo. They would have put my levels up above 20, so you were lucky if you leveled out at 10! You do need to be careful though because if this was a Reactive Hypoglycaemic incident then those penguins could easily have triggered another high and then another reactive low, so you could end up on a really nasty rollercoaster.
I would choose a lower carb breakfast in the future and make sure you have a portioned out 15g treatment handy in case it happens again, so that you are not temped to overtreat. Reactive Hypoglycaemia is not very common but it can happen when people are just developing Type 2 diabetes I believe and it can in fact drop you well below 4, so it will be particularly important for you to avoid high carb foods in case it triggers another episode. Most people with RH control it by eating little and often and avoiding carb rich foods or just having very small portions of them at any one time.