The 26-year-old, who made his last appearance for Ireland as a second half replacement against Canada in 2000, was chosen for the side by Sky Sports pundits Stuart Barnes and Dewi Morris.
Kildare-born Casey scored his first try for Irish last month in the 25-20 win over NEC Harlequins, has made 21 league starts for the club in 2004/05 and also played all 80 minutes in last weekend's 23-16 loss at Newcastle.
The bonus point the Exiles picked up at Kingston Park helped them remain in the Premiership - their closing tally of 40 points being just two ahead of the relegated Harlequins.
Sky Sports Premiership Dream Team 2004/05:
Andy Beattie (Bath), Chris Bell (Leeds Tykes), Duncan Bell (Bath), Bob Casey (London Irish), Sebastien Chabal (Sale Sharks), George Chuter (Leicester Tigers), Mark Cueto (Sale Sharks), Ayoola Erinle (London Wasps), Craig Gillies (Worcester Warriors), Andy Goode (Leicester Tigers), Matt Powell (Worcester Warriors), Bruce Reihana (Northampton Saints), Graham Rowntree (Leicester Tigers), Pat Sanderson (Worcester Warrior) (Capt), Scott Staniforth (London Irish).