The PPT is the "plunge Protection Team". I don't think that they are in the market as often as some of my cyberfriends here think, but at critical junctures, and when markets risk becoming "disordered", they provide liquidity of last resort. They publicly admitted of having done that in October of 1987 and during the Russian malaise and the Asian Tigers malaise. Who knows how many other times, but these have been documented (secret phone calls and meetings, usually directed by Greenspan and carried out by the the person heading the Federal Reserve Bank of NY, typically in conjunction with the five largest US banks and the largest brokers).
Zeev