Oh chipmonkey, the number of times got that one and responded 'I don't come to your party, you don't have a party'!!
(and mm, your ds4 really is rather lovely, and I'm not remotely keen on babies these days!)
Friendship politics are quite trying at 4, I think - and I have a DD, so I expect that side of things to last, ooh, fifteen years or so? DD has also had screaming tantrums since turning 4 that she'd never had the likes of before - 'fortunately' the frightens the life out of herself quite quickly and ends up clinging to me for solace.
DD had a little friend at her trampolining class for a while, I got to watch the 4yo boy testosterone surge from the sidelines there. Wow. He was a sweetheart a lot of the time, but there were times when there was just NO reasoning with him. Even the coach, ex-nanny, astonishingly good at getting small children to do her bidding, had to just leave him to it.