Bones, the in-house mentor for the singing competition, filled in for Seacrest when Monday night's episode filmed a few weeks ago after Seacrest had fallen ill.
"I am not Ryan Seacrest. I am Bobby Bones," Bones, 39, said in a sneak peek clip, poking fun at the physical similarities between himself and Seacrest. "Sadly, Ryan is sick and I look most like him so they asked me to fill his shoes tonight. Ryan, love you, buddy, hope you get better."
He continued, teasing the second round of Idol's All-Star duets. "It's round two of our All-Star duet round and, man, do we have a lineup for you tonight. We are joined by six singing superstars who will be teaming up with our super talented contestants for some show-stopping duets."
During an appearance on Seacrest's morning radio show, On Air with Ryan Seacrest, Bones made an appearance and opened up about a fun gift he received from the longtime Idol host: a pair of shoes with a note that said, "Thanks for filling my shoes."
"Bobby was kind enough to fill in for Monday's episode which we taped a few weeks ago, and I'm thinking, you know, the guy stepped in last-minute, did a great job. What do I get him?" Seacrest said on the show. "I got him some shoes!"
Bones is used to wearing many hats on ABC, as he recently won season 28 of Dancing With the Stars with pro dance partner Sharna Burgess, and even revealed he had an inkling he might be approached by the network about becoming the next Bachelor.
"I was approached a few months ago, asked if I would entertain the option of being the Bachelor and I said no because it definitely wasn't an offer. It was, hey, is this something you'd want to do," Bones said on The Bobby Bones Show in March 2018, a few months before he joined the cast of Dancing With the Stars.
Months later, in September, he brought up the topic once again. "Listen, I'm gonna tell ya, if I go far on Dancing With the Stars, they're going to offer me The Bachelor, I can already tell you."
After he flat-out won the ABC reality dance competition, Bones didn't immediately squash rumors he was the next Bachelor. When Good Morning America co-host Michael Strahan asked Bones about it the morning after the DWTS finale, he said, "I'm in."
During Sunday and Monday's American Idol episodes, all-star musicians like Ben Harper, Julia Michaels, Shaggy, Lucas Graham, Chris Isaak, Cynthia Erivo, Brett Young, Jason Mraz, Pat Benatar & Neil Giraldo, Elle King and Lovely the Band will join forces with the top 20 contestants to perform powerful duets.
American Idol airs Monday at 8 p.m. ET on ABC.