Simon Cowell missed The X Factor's first live show on Saturday night as he rested at home after falling down the stairs.
The judge was rushed to hospital on Friday after he took the tumble in his London home, but was photographed flashing a "thumbs up" when he returned hours later.
Introducing the judges, host Dermot O'Leary told viewers: "Thankfully three of them made it," adding: "You might have spotted one judge is missing - that was because Simon was taken to hospital yesterday.
"But he's doing fine, he's back home, he's watching the show," he said, adding: "Get well soon, boss."
Not put off by his absence, the three judges joked they were innocent over the incident as O'Leary asked which of them had "put the banana skin at the top of the stairs?"
Louis Walsh said he was downstairs boiling milk, while Sharon Osbourne quipped she was "in the library with the candle stick".
Nicole Scherzinger said: "It was a team effort".
The first live instalment of the singing competition saw the hopefuls tackle the theme of Express Yourself, and the judge's four wildcard acts were also revealed.
Alisah Bonaobra, Leon Mallett, Jack & Joel and Talia Dean were the four acts to return to the competition.