Do you usually do it at the Micros?

Example : You hold KK . Raise pre, they call.

flop : 2 4 9 rainbow

you bet, they shove (overbet)

whats your play?

I usually sometimes do it, and I usually sometimes don't. It depends.

Your example is missing a whole bunch of critical details. A villain jamming their entire stack into a single raised pot like that looks fishy as hell, which would be one reason for calling. But no way I can say what I'd do without more information, this is extremely situationally dependant.

in that specefic example (assuming 100bb), call.

In this case I would call, because in my experience when a player takes a line which makes no sense they are weaker. With the exception of river overbets (those tend to be the nuts more often), I usually find overbet shoves like this to be spewy.

However, if he called or c/c the flop, then raised you on the turn I would be more likely to fold (assuming no reads etc). At the micros, turn raises/check raises after calling on the flop are much, much stronger than flop raises

These answers are why I sometimes hugely overbet the nuts on the flop. I almost always get called by regs or fish.

Depends. I sometimes take this line if I hit a monster and I'm sure villain is really bad, has an overpair and can't let go.

It's really villain and stack-size dependent 100 BBs+ deep. Generally I stack off if villain has a low SPR ratio and his shoving range is wider than usual.

It depends, it depends, it depends.

What are the stack sizes? If I'm short, or my opponent is short, I'd be more inclined to stack off with an overpair on a raggedy board. Deeper, not so much. When the stacks are deep, then it's time to think pot control. It may be better to x/call three streets, depending on how you read the vill, and hope he didn't do something stupid like call pre with a ( 9,2-off ) (they do that sometimes).

It's also a very villain dependent play. Sometimes, you have yutzes who'll likely do something really stupid, like make desperation AI bluffs. I've seen this with some of the damnedest hands. Sometimes, you have players who know what they're doing. Is it possible the vill could call with odds with a smaller pocket pair? Could he be making a play like that OTF, or would he be more inclined to slow play, especially on a low, dry board? Paying attention pays dividends, even at the Micros.

Sometimes, you call and you get shown a white blackbird. Oh well... them's the chances you take when you buy into Microstakes.

If you are talking about simply open shoving the flop with top two+, this is possibly a valid strategy against most players at least once.

IME 95%+ of the time this line is a weird 2 pair hand, TPWK, a draw or air. I hardly ever call and see a really strong made hand.

the one problem I have with overpairs sometimes is getting called by a smaller pair and them spiking a set and getting it all in dominated after the flop