Baddiel and Skinner Unplanned was broadcast on ITV and ran for 60 episodes between 2000 and 2005. It was basically a kind of early podcast format, in front of a theatre audience (London Studios).

If you want to know how “two blokes, one sofa, no script” went, Avalon (production company) have posted S1 Ep1 here. That first episode was broadcast on May 28^th 2000

Frank also had his own BBC show (between 1995 and 2005, called The Frank Skinner Show) but the tiny number of comments I’ve been able to find suggest that Jimmy’s role as warm-up man was on Baddiel and Skinner Unplanned.

There is a post on this forum from someone that says:

I went to see Baddiel and Skinner Unplanned being recorded and he was their warm up act

Early press articles about Jimmy (such as this 2002 Newsshopper one) also regularly mentioned:

He cut his teeth working as a TV warm up man for Baddiel and Skinner and Al Murray, but his witty deconstruction of modern living has established him as a comic in his own right.

This BBC web page (which was from 2002 and not 2014 as it now states) says:

Not only does Jimmy appear in numerous television roles he also regularly warms up for the Frank Skinner Show, Baddiel & Skinner Unplanned, Alistair McGowan, Al Murray’s Time Gentlemen Please and the Alan Partridge Show amongst others.

And Comicus (a business that hires out guest speakers and performers) have an old Jimmy Carr profile (here) that says he was a writer for Frank. I’ve not seen that anywhere else – but it’s entirely possible and, while not relevant to the warm-up role, shows another link to Frank, from the early days (he also did warm-up for Frank – here):

Jimmy is a prolific writer as well as performer, with writing credits including Bo’ Selecta! (C4) & Meet Ricky Gervais (C4) as well as writing for Lily Savage and Frank Skinner.

All of which leads me to assume that Jimmy was probably the B&SU warm-up for S1 in 2000. Warm-up comics are rarely logged by shows (so it’s impossible to be more specific) but, by 2001, Jimmy had started working for E4 channel (here) so it’s likely that his warm-up days were over by then.

What I can virtually guarantee is that he will have been soaking up how TV shows were put together. He didn’t get to have such a massive body of TV work (here) by just turning up and taking a cheque. Every day’s a school day.

Around 1999-2000 he was warm-up for a handful of shows – see more here.