Here's two names we thought we'd never cobble together in a sentence: Ludacris and Justin Bieber. The rapper and the 'tween star combined forces to come up with "Baby," the first single from Bieber's forthcoming "My World (Part II)," due in March.

The bullet-fast rhyme-slinger has been trying to make impact of his own in the Hot 100 with his track "How Low," but, this new collaboration with newcomer Bieber is already No. 2 on the iTunes download chart, which may amp this "Baby" up to No. 1 soon and onto your radio station's playlist.

"Chuck Norris bought BABY on ITUNES infinity times....twice" Bieber Tweeted today. Ah, that explains it.

Luda contributes only a few "ohs" and a single verse waxing nostalgic on his first love, when he was 13. Justin's alto voice delivers his typical R&B-tinged croonings with a dance beat backing him.

We only regret we have no photo of Ludacris leaning on the handlebars of his bicycle. His new album "Ludaversal" is due some time this year.