Lulu was a prostitute, but she didn't want her grandma to know.

One day, the police raided a whole group of prostitutes at a sex party in a
hotel, and Lulu was among them. The police took them outside and had all
the prostitutes lined up along the driveway when
suddenly, Lulu's grandma came around the corner.

Grandma asked, "Why are you standing in line here, dear?"

Not willing to let her grandmother know the truth, Lulu told her grandmother
that the policemen were there passing out free oranges and she was just
lining up for some.

"Wow, that's awfully nice of them. I think I'll get some for myself", and
she proceeded to the back of the line.

A policeman was going down the line asking for information from all of the
prostitutes. When he got to Grandma, he asked, "Wow, still going at it at
your age? How do you do it?"

Grandma replied," Oh, it's easy, dear. I just take my dentures out, rip the
skin back and suck them dry."

The policeman fainted.