McCarthy has named a strong starting lineup for the 19:00 GMT clash, with an interesting mix of regular starters and slightly younger faces on the bench, including Kanye Jobson and Joseph Ling.
Fans will likely recognise starters Tayo Adaramola and Fionn Mooney from signing their recent professional contracts.
Defender Noah Watson has competed with the Under-23s this season while Cardo Siddik and goalkeeper Owen Goodman have international experience under their belts.
Frontman David Omilabu is likely to be one to watch this evening after scoring seven goals already in 2020/21.
McCarthy's Eagles currently sit fourth in the U18 Premier League South and you can brush up on all you need to know before the cup game with our preview here.
Tonight's match will be broadcast live via Fleetwood Town's YouTube page - you can watch it from 19:00 by clicking here.
Palace: Goodman, Thisleton, Watson, Steele, Siddik, Quick, Adaramola, Wells-Morrison, Mooney, Akinwale, Omilabu.
Subs: Whitworth, Jobson, Rak-Sakyi, Gonzalez, Raymond, Cadogan, Ling.