Willie Aames -- Robbed at Gunpoint!

TMZ has learned actor Willie Aames -- yeah, Buddy from "Charles in Charge" -- and his son Christopher were robbed with the help of a silver steel automatic handgun.

At around 10:00 PM last night in Hollywood, a man wearing a black jacket and blue jeans approached Willie and Christopher, pulled a gun and demanded money. They forked over a wallet and loose cash. Total damage -- about $15! Willie and Christopher were unharmed.

We're told the robber fled the scene in a black car. A popo investigation is underway. Willie's rep tells TMZ, "Willie is in town to shoot a celebrity reality show for VH-1. He credits what he's learned on the show in helping him to remain calm during this situation."