Although raising funds for a serious cause, the song was full of laughs and Marvelly said she couldn't wait for everyone to see it tonight.
"I can't wait for everyone to see some of the footage. Flight of the Conchords were interviewing, they went around and interviewed kids. You know what kids are like, the things they say - we just had a great time. It's always awesome to catch up with all the people in the New Zealand music industry and for such a good cause."
McKenzie and Clement had spent the night before the recording session writing lyrics and Marvelly said they did an "amazing job".
The song will premiere during the four-and-a-half-hour live show, which will be hosted by comedians and 7 Days regulars Jeremy Corbett and Paul Ego, and include performances from New Zealand's top comedy talent and pre-recorded footage with everyone from the All Blacks to a special reunion of the cast of Outrageous Fortune.
McKenzie, Clement and Marvelly will be joined by Brooke Fraser, Dave Dobbyn, Anika Moa, and hip-hoppers Savage and PNC, among others in the Kiwi music supergroup.
Event director Brooke Howard-Smith said the song was basically a We Are The World-style song with guest appearances from "everybody we could find".
She said the show was kind of like a mini-Telethon, although shorter with a comic relief focus.
One hundred per cent of the donations will be invested into medical research into child health.
Red Nose Day: Comedy for Cure Kids airs tonight on TV3 from 7.30pm. The song will be available to buy from iTunes after 10pm.
- Additional reporting APNZ