Help Identifying a Leak (Engine Block Coolant Drain Plug?)

Leaks are......'interesting' .... at least to me.

Submariner's rule:
If you find it?
It's a leak.

If it finds you?
It's flooding.

So.....
What's 'leaking?"
Oil?
Coolant?
Rain water?
Transaxle Fluid?

How much are we talking about??
It is a weep? seep? drip? dribble?

They each have individual meanings.

Where is the car parked?
In a garage?
Driveway?
An 8oz cup of fluid is....a LOT.
Spill a full cup of coffee onto your kitchen floor and you will know what you know....

What's in YOUR gargae?
Driveway?

Deets!!!!
Are you the original owner?
Does the phrase "EGR cooler" mean anything to you?
What's the coolant level? Oil? Coffee carafe?
Has the bottom end of the engine been replaced (yet?)
Maintenance history?

If you're the 2nd (or 3rd....4th...etc...) owner then you must presume that 'your car' has a 'history.'
This is nothing to be ashamed of.
We all have 'histories.'

PRESUME that YOUR car has its original head gasket, plugs and coil packs, oil filter, and that the EGR circuit hasn't been cleaned.
PRESUME that this is a factory-maintained vehicle, and that you're 80,000 miles past the extended factory warranty period - which means (according to Toyota's philosophy) that they've met their obligation to produce a 'good' car.

Me?
I'd start looking at fluid levels more often and I'd replace the plugs IMMEDIATELY - not because the plugs are wrecked but rather to give you the opportunity to look at the plugs and maybe invest $50 in a borescope, and maybe look into the holes.

Also...
If you start to get the "Prius Death Rattle" ......STOP DRIVING IMMEDIATELY.
You will not have to wonder if this is occurring.

Good Luck!!!