Stereophonics star Kelly Jones has joked the band didn't just want Sir Tom Jones on their Principality Stadium bill because of his "incredible" voice, but so he could return his plate.
He was given a take-home brownie by him after going to Sir Tom's flat to watch Wales play in football's Euro 2020.
More than 80,000 are due in Cardiff on Saturday for the weekend's second Stereophonics gig, as well as the Tafwyl festival in Bute Park.
Fans are urged to travel in good time.
The Welsh government and public transport operators have advised people heading to Cardiff to plan ahead because roads and trains around south Wales will be "very busy".
Authorities want to avoid the travel chaos ahead of the Ed Sheeran concerts in Cardiff last month - although there were no major issues on the road for Friday night's show.
'I've got to give Sir Tom his plate back'
Kelly said he invited Sir Tom to support the band not just because he's "unbelievable" and like a "second father" but it was a chance to give the Welsh singing legend his crockery back.
"I was watching the football with Tom over the summer, I'd go to his apartment and watch the Wales games and I gave him a ring to see if he'd fancy it," said the Stereophonics frontman.
"It's for the Welsh people, something for them to look forward to and celebrate - and he said he was bang up for it.
"It was also an excuse for me to take his plate back because he gave me a pudding that night watching the football, a brownie at one o'clock in the morning, and I never took his plate back."
Sir Tom and the Stereophonics are among Wales' most famous musicians and their cover of Eric Burdon's hit Mama Told Me Not to Come in 2000 reached No 4 in the UK charts.
These shows are the first time Sir Tom, whose hits include Delilah, It's Not Unusual and Green, Green Grass of Home, has played at his home country's biggest concert venue.
"He's been a friend and second father to me for 20 years, giving me advice and anecdotes," added Kelly, 48.
"At his place, he was showing me pictures on his wall, him with the likes of Aretha Franklin to Elvis.
"We've also been watching footage of him singing with Little Richard and Jerry Lee Lewis - the man has shared a stage with everybody and held his own, if not done it better. It's an honour to have him on our bill."
Music fans advised to travel early
People attending the gigs have been advised to leave extra time for the journey to Cardiff with the M4 motorway across south Wales also expected to be congested.
Travelling to see Stereophonics this friday & saturday?— Traffic Wales South (@TrafficWalesS) June 16, 2022
Daily traffic flows on the #M4 from J28-29 increased by 18% on average during the Ed Sheeran concert. 📈
Traffic peaks on the M4 were between 1pm-7pm👀⬇️
This weekend, plan ahead & leave earlier to avoid delays & stress. pic.twitter.com/dg3mE7biKv
Roads in Cardiff city centre will be shut from noon on Saturday on "health and safety grounds to ensure people can safely enter and leave the stadium".
Rail passengers have also been told that all services around Cardiff will be busy and trains will be at full available capacity.
While Transport for Wales acknowledged it faced "challenges", location data from concert ticket sales suggest that about "70% of concert-goers and coming from the Cardiff, valleys and Swansea area".
🔊Hoffwn atgoffa cefnogwyr @stereophonics bod system giwio yn ei le yng Ngorsaf Caerdydd Canolog.— Trafnidiaeth Cymru Trenau Transport for Wales Rail (@tfwrail) June 17, 2022
Mwynhewch y cyngerdd🎸
🔊@stereophonics fans are being reminded that a queuing system will be in place at Cardiff Central Station.
Enjoy the concert🎸 pic.twitter.com/bBxItluVhL
Railway upgrade work and unnecessary roadworks on the network in south Wales have been suspended for event weekends at the Principality Stadium but travellers have been urged to plan ahead.
What time does the concert start?
Super Furry Animals frontman Gruff Rhys will also support on Saturday - with Sir Tom Jones starting his set at 18:05 BST while the Stereophonics will be on at 20:00.
Gates to the Principality Stadium will open at 15:00 and the first act is Welsh group Buzzard Buzzard Buzzard who will start the show at 15:40.
Noel Gallagher plays Colwyn Bay
Former Oasis songwriter Noel Gallagher will also play in Wales on Saturday evening at the Eirias Stadium in Colwyn Bay.
Welsh rock band Feeder, whose hits include Buck Rogers, Just A Day and Just the Way I'm Feeling, and The Vaccines will support Gallagher at the 15,000-capacity event.
Gates open for the Colwyn Bay concert open at 16:00 while the Don't Look Back In Anger and Wonderwall singer is expected on stage at 20:30.
People have been warned the A55 along the north Wales coast and local trains are expected to be busy.