A man told his doctor he couldn't stop singing Tom Jones songs.

This doctor joke hinges entirely on a clever bit of wordplay, specifically a pun. The humor comes from the doctor's response, which sounds like a professional medical assessment but is actually a direct reference to the iconic 1965 hit song "It's Not Unusual" by Welsh singer Tom Jones. The punchline relies on the listener recognizing the song title, creating a moment of unexpected recognition and a chuckle as the two meanings collide (Review).

"It's Not Unusual" was Tom Jones's first major hit, reaching number one on the UK charts and cracking the Top 10 in the US. The song is known for its brassy arrangement and Jones's powerful vocals, and its title phrase has become a well-known idiom, meaning something that happens frequently or is not out of the ordinary. This widespread familiarity with the song is crucial for the joke to land, as it provides the real-world context that makes the pun so effective. The doctor isn't diagnosing a rare illness; they're simply completing a famous song lyric, much to the patient's (and audience's) amusement.