"Bullfrog Does Oral Sex" joke

An attractive woman entered a pet shop. When the clerk offered assistance, she explained that she was recently divorced, and was looking for a small-ish dog for company.
The clerk explained that the name of the store was 'Exotic Pets' and that, unfortunately, they did not stock cats, dogs, fish or any commonplace pets.
He did say, however, that he had something which might be ideal. He took the woman into a back room. He walked over to a terrarium, and pointed proudly to a large bullfrog which sat inside it.
"Would that suit your needs?" he asked.
The woman answered, scornfully, that she hardly thought an amphibian would be a suitable companion.
"Ah," replied the salesman, leering, "but this 'amphibian' has been carefully trained... to perform oral sex upon women."
At this the woman's eyes lit up.She eagerly negotiated a price of $500 for the frog, and left with it in her expectant possession. Arriving home, she drew a bubble bath, poured a glass of champagne and relaxed in anticipation. When she was thoroughly mellow, she dried herself, and arranged herself, nude, upon her bed. Parting her thighs, she placed the frog between them, closed her eyes, and waited.
Nothing happened. She prodded the frog. Still nothing. She moved it Up further toward her body. Nothing. She ordered it to perform. No response.
After an hour of this frustration, she lifted the phone, and called the pet shop. When the clerk answered, she complained loudly that she had been cheated. The clerk apologized profusely, wrote down her address, and said he'd be right over.
Ten minutes later, he knocked on the door, and the woman answered, wearing a nightgown. He asked her to demonstrate the problem. She obliged, by disrobing and assuming her former position, with the frog in place. The frog made no movement.
"You see?" she asked, petulantly.
"Yes, I do," said the man.
Then, addressing the frog as he removed his necktie and shirt, he said, "Now, I'm only going to show you this one more time..."