Arnold Schwarzenegger Pranked with 'Arnold's Maid' Ski Run in Idaho -

Some hooligan had some fun at Arnold Schwarzenegger's expense ... taking a shot at the former Governator's indiscretion by defacing a decades-old sign.

It all went down at Idaho's Sun Valley Resort where the Terminator had "Arnold's Run" named after him back in 2001. It used to be the "Flying Maid." You can see where this is going. Some dope riding down the slope decided to change it to "Arnold's Maid" ... a clear shot at Arnold fathering a child outta wedlock with his maid.

A spokesperson at the resort tells TMZ ... they did notice the vandalism and have addressed it. We're told the sign's been fixed and it's now back to "Arnold's Run."

Looks like they got it changed just in time, because Arnold was up in Sun Valley on Monday and said he went skiing before a bike ride.

As for why the Idaho joint chose to honor the actor ... Arnold makes regular getaways up there. He's also previously led the Christmas Eve torchlight parade down the mountain. They love him.

And, what's love without a little poke of fun?