I looked up the word "picture" in the dictionary and it is usually said "Picture someone doing something". Shouldn't the word "engaged" be "engaging" in the following sentence?
Perhaps you’re obsessively picturing him engaged in drunken coitus with another woman.
This line was said by Sheldon Cooper, who hardly ever makes grammatical mistakes, so I am pretty sure it is grammatically correct what he said, but I don't know why he said "engaged" instead "engaging". Please highlight the difference. Thanks.