Frankel enjoyed an imperious 11-length triumph in the Queen Anne Stakes last year on his way to becoming the world's highest-rated racehorse.
The memory of that explosive victory will have extra poignancy following the death last week of Frankel's trainer Henry Cecil, who trained a record 75 Royal Ascot winners over four decades.
"I'll never train another one like him. The horse has had a chequered career because of his injuries so it is all the more remarkable how he has kept his form," Animal Kingdom's British-born trainer Graham Motion said of the 2011 Kentucky Derby winner. Motion now keeps his barn at Fair Hill in Maryland.
Animal Kingdom will be retired to stud after Tuesday's race.
"Royal Ascot is a bonus for me because I thought Dubai was his last race. I feel very fortunate that these guys have taken on this very sporting challenge at Royal Ascot," Motion said. "It's tremendous to be running in a race that Frankel won last year and Sir Henry Cecil was one of the people I admired the most when growing up in Newmarket so it's quite emotional."
Animal Kingdom, who will be the morning-line favorite and is by far the highest-rated horse in the Queen Anne, has never raced over a straight mile course that he will encounter at Ascot.
Motion said they were going into "unchartered territory" with a horse that has not run since March's Dubai success.
"There are so many variables. The weather, distance and doing the training here are all different. Animal Kingdom is a really laidback horse, like an old steeplechaser," he said.
The Queen Anne is the first of three successive Group One races to start the prestigious five-day meeting, with the King's Stand Stakes followed by the St James's Palace Stakes in which Epsom Derby flop Dawn Approach attempts to restore his lofty reputation.
Ascot will honor and celebrate the memory of Cecil by naming the Queen's Vase, run on Friday, after the trainer. Cecil's wife Jane, who has temporarily taken over the training license, is set to have a runner in the race.