Called me, leaving automated message from 'IRS' filing lawsuit against me. And to call 202-864-1201 for case details.

Total scam.   Originates in India.

See:  http://www.irs.gov/uac/Newsroom/IRS-Reiterate ... -Telephone-Scam

Fraud.  Don't answer them.  IRS never calls you.  IRS write to you in case if there is a dispute.  If you go to IRS website you
will find it.

Recorded message when I picked up.  The biggest tip was when the lady on the recording said they are the "Internal Revenue Services"  (plural).

I didn't even write down the number she wanted me to call.

Low-life scumbags.  There should be more aggressive investigation/prosecution against these a-holes.  I know most of them are outside U.S. jurisdiction, but let's start with the woman who recorded the message. She was clearly speaking with an American accent.  Start by finding and bringing charges against her.

Left a message that was same as what others have stated - that they are the IRS, are filing a lawsuit against me and for me to call 202-618-1898 (a VoIP number in DC area).  
The call was displayed as from 712-201-5286 (bogus spoofed number listed as from Sioux City in Iowa).  The 712-201-xxxx part comes up often in 800Notes connected to various scam calls.  

I will file a complaint with the IRS and FTC.  

I would certainly like to call these scum suckers back to have a friendly(!) conversation with them, but my better side is preventing.

Stay diligent, they are out there...