I know exactly what you're talking about, OP. And yes, I also love it when it happens in Britney's songs! I've always thought of it as being incredibly clever and interesting and adds a special flavor to the song. However, I've always wondered something, is there a special term/name for this...thing? I want to look it up on Google, but I always have trouble finding the words to describe what I mean.
List of Britney songs that do this:
BOMT
I Will Be There
You Drive Me Crazy (Stop Remix)
OIDIA
Lucky
Stronger
One Kiss From You (kinda sorta)
Can't Make You Love Me
What U See Is What U Get
Don't Go Knocking On My Door
Cinderella (Doesn't really go into the final chorus though unless I'm hearing it wrong)
When I Found You (Kinda sorta again)
I kinda wish Britney would do this still since she hasn't done it in years...and it's done in some Backstreet Boys and Nysnc songs too. I also heard an A*Teens song that had the exact formula as well. If anyone can name songs that also do this it would be appreciated.