At around 3am today

have an RPM

It wasn't a click bomb,

And after those 2 clicks the value went back to normal.

Intra-day RPM is based on the number of impressions that have been recorded since 12:00am. At 3am there have been very few impressions. A single click, early in the day (middle of the night) can cause intra-day RPM to spike. Say in the first hour you have 100 impressions and one click of 1$ then that works out $1/100 impressions or and RPM == 10$/1000 impressions. As the day proceeds impressions and clicks will continue to be recorded at the normal rate and reported RPM will revert back to its mean (average). This "side effect" can be further exacerbated by getting a high value click.

So long as things revert back to normal, and there is no signs of click bombing, there should be no need to worry. Generally if there is some kind of error or unusual click pattern Adsense is pretty good at rolling that back.

At the time, the ad units had had something like 200 impressions each. I usually either get a lot of Ebay ads or passbacks to my back ups, so it's hard to imagine someone was bidding $50 for a single click at that time. And not once, but twice!

But Google hasn't done anything or said anything yet, so...

revenue = $20
impressions = 200
Revenue per 1 impression => $20 / 200 = $0.10
Revenue per 1000 impressions => $0.10 * 1000 = $100

One doesn't get $20 clicks everyday but they do occur on occasion. I've had a few over the years.