Allaho missed all of last season but returned to win the Clonmel Oil Chase this term setting him up for a tilt at the race considered only second to The Cheltenham Gold Cup over jumps.
He faces just five rivals, including defending champion Bravemansgame and the sublimely talented but unpredictable Shiskin described as a "bit of a plonker" by his venerable trainer Nicky Henderson.
Allaho sat out last season - after winning a second successive Ryanair Chase at the Cheltenham Festival in 2022 - with a rare spleen complaint.
Mullins, 67, was happy enough with the horse's performance in winning in November to aim him at the King George, a race the trainer won with Florida Pearl in 2001 and Tornado Flyer in 2021.
His son Patrick, who is his assistant, says they expect a big run from the favourite although he added a caveat.
"Since he won the Punchestown Gold Cup and showed he can stay three miles, the King George has definitely been on the radar, and with his owners (Cheveley Park Stud) it's a nice fit," said Mullins on Saturday.
"He's nine, going 10, coming back from a year off the track, so it's hard to think he's still at his very best, but hopefully he might still be good enough to win."
'Hunting horn'
Both Bravemansgame - who if victorious would give trainer Paul Nicholls a record-extending 14th win in the race - and Shishkin come into the contest on the back of disappointing displays.
Bravemansgame looked a shadow of the horse that won last year's King George by 14 lengths and finished an excellent second in the Cheltenham Gold Cup in March as he filled the runner-up spot in the Grade One Betfair Chase in November.
Nicholls, though, thinks the horse will be better for that run - which followed another runners-up spot on his debut this term.
"Bravemansgame won the race last year and then the season before he won the Kauto Star (Novices' Chase) around Kempton," said the 61-year-old.
"He loves it there and it is the ultimate track for him. It is almost a home game for him in many ways.
"Whether the Gold Cup left a mark on him I don't know, and it could be that it has just taken a while to get him back.
"What have we got coming from England to take him on? There is Shishkin, who has got a question mark next to him.
"Allaho came back and won the other day from his time off, but is he as good as he was?
"The previous year's winner of the race is always the one to beat."
Shishkin certainly does have a question mark hovering over him as he dug his heels in and refused to start his last race at Ascot.
Henderson says he is confident Shishkin will at least give his supporters a run this time as the trainer's assistant will go down to the start with him.
"I'm not going to sit here and tell you he can win a King George, but I do think he can run very well," said the 73-year-old.
"He is the sort of forgotten person in the race, and no one has mentioned him.
"Charlie Brooks mentioned a hunting horn to ensure he started, but Barney (Clifford, Clerk of the Course at Kempton Park) won't let me get up a tree and blow it!"
