The woman, who was Jackson's personal maid for about five years and whose son settled a molestation claim with the singer, told of seeing Jackson in the shower with a boy about 8 years old who frequently stayed at Neverland.
"Are you aware of him staying anywhere other than in Michael Jackson's bedroom?" asked prosecutor Ron Zonen.
"No," said the woman, speaking with a Spanish accent. "He stay there."
The woman was called to the stand in Jackson's child molestation trial Tuesday after her son came under tough cross-examination about his story of being molested three times more than a decade ago. He received a $2.4 million settlement from Jackson in 1994 after claiming the pop star groped him.
The woman was part of a prosecution effort to show that Jackson has a pattern of molestation or inappropriate behavior with boys, which could add credibility to the current accuser's molestation allegations.
"It's not just the number of witnesses who are coming forward it is the detail they are offering," said CBS News Legal Analyst Andrew Cohen.
"Even if these jurors don't believe everything that prosecution witnesses say, they probably believe enough to see patterns in Jackson's behavior; sinister patterns; and that is a problem the defense is going to have to find a way to overcome," Cohen said.
Jackson is accused of molesting a 13-year-old cancer survivor in February or March of 2003. The case was scheduled to resume Thursday after a break Wednesday.
Before the former maid took the stand, defense attorney Thomas Mesereau Jr. raised the issue of whether she had a financial stake in his story by showing she had been paid $20,000 to appear on the TV show "Hard Copy."
The woman testified that one day she used a key to enter Jackson's bedroom and heard "laughing, playing — like playing around."
"First I thought they were playing in bathtub or Jacuzzi or outside in his garden and I walked in and they were in the shower," she said, adding later, "I peek in and they were in shower."
The woman said she saw their clothes on the floor outside the shower but retreated because she thought Jackson would be mad if he found her there.