It is absolutely real, the MH-53 Pave Low is regularly trained in the Israeli and US forces for air-air refueling. The important part is maintaining sufficient airspeed so that the C-130 (or other aerial tanker) doesn't drop out of the sky.
Lots of helicopter types (even Chinook's) can be air refueled but not every country has the ability to do it. It takes balls and skilled pilots on both ends.