Is this some kind of controlling Mummy game? If DD (20months) really really wants something, and I give it to her, more often than not lately she'll throw her hands up and shout "no, no, no!" (read: how dare you insult me by giving me that thing that I so desperately wanted 10 seconds ago, Mummy!)
Please tell me she's not the only one with this seemingly deranged behaviour.
You appear to have DS2's twin! We have this conversation most breakfast times - "cheerios, cheerios, cheerios, no, no no, shreddies!" Maybe he's seeing how high he can push my blood pressure before the top of my head blows off, cartoon volcano style