Ant and Dec, who could be on course for their first number one single, resumed their musical activities "for a laugh", they have said.
The popular TV duo might be in the top spot on Sunday, 17 years after their chart career came to an end.
The pair prompted a download dash for their 1994 hit Let's Get Ready To Rhumble when they performed the track on their Saturday Night Takeaway show at the weekend. It quickly went to the top of the iTunes chart and on Tuesday the Official Charts Company confirmed it was leading the pack for Sunday.
Ant McPartlin told ITV1's Daybreak programme that they were short of an item for the show. "We thought, well, we could possibly dust off the old baseball caps, and give it a go, for a laugh.
"The production team on Saturday Night Takeaway went mad, 'oh yeah, we remember that song, let's do it'.
"We thought, 'well, it'll be a bit of a laugh, let's do it'. Never expected it would be number one in the midweek charts."
Declan Donnelly said: "We did a little bit of rehearsal on Thursday, we had four hours in our schedule, to rehearse the dance. We spent an hour, and it all came back to us. We've obviously done it so many times in the past."
Ant added: "We're conditioned into doing it."
Dec confirmed that money from the revived hit would go to charity. He said: "At 20 past eight on Saturday night when the show finished we thought we'd fold up our hockey tops and that would be the end of it, and that'll be it, and it's gone mad. We got to Monday, the weirdest weekend, people were buying it, we thought, we can't take any money from this, anything we do, we'll give to charity."
By Tuesday the track had sold 35,000 copies, though it would have to keep up the momentum all week to be in with a chance of ousting current number one The Saturdays with What About Us. Ant and Dec had a run of hits in the mid-1990s, with nine songs in the top 40. Let's Get Ready To Rhumble was their only top 10 hit, peaking at nine.