Munster wing Earls led out his country alongside his three daughters on Saturday evening in Dublin before marking the occasion in style by coming off the bench to seal a 29-10 victory with a superb diving finish.
The 35-year-old received a host of touching tributes ahead of the landmark appearance at the Aviva Stadium, while his family were invited into camp on Thursday.
Earls went a year without international action due to injury issues before lining up against Italy at the start of the month but insists he did not return solely on sentimental grounds as he eyes a place on the plane to France.
“That’s the reason I’m here, that’s the reason I came back for pre-season, that’s the reason I’m doing everything possible to stay fit,” he said of World Cup selection.
“I have that burning desire to give myself the best chance of going to the World Cup and I tell you one thing I’d hate to be the coaches trying to pick their 33-man squad. It’s going to be tough.”
Andy Farrell is due to reduce his squad by five to a final 33 following next weekend’s clash with Samoa in Bayonne.
His Six Nations champions registered a 12th consecutive win by comfortably dispatching Steve Borthwick’s side.
The unassuming Earls, who added to scores from Bundee Aki, Garry Ringrose, James Lowe and Mack Hansen with his 36th Ireland try, felt a little uncomfortable in the spotlight and feared being left embarrassed as an unused replacement following the big build up.
“I was saying to the lads, it was probably the worst week of my life with all the attention around the 100th cap,” he said.
“It was the hardest thing I’ve ever done on Thursday trying to keep the tears out of my eyes around all of the lads.
“But I think I managed to do it, so that was grand.
“I’m delighted everything worked out perfectly and there’s not a better bunch of lads to do it with.
“It was hell sitting on the bench. It was nerve-wracking, thinking: ‘will he put me on? This will be very embarrassing after everything I’ve gone through’.”
In addition to receiving video messages from the likes of Ireland great Brian O’Driscoll and former coaches Declan Kidney and Joe Schmidt, Earls was presented with his milestone cap by head coach Farrell, while captain Johnny Sexton and forwards coach Paul O’Connell gave speeches.
A more offbeat homage came from team-mate Hansen, who shaved the initials KE and the number 100 into an eye-catching green haircut before claiming the man of the match award against England.
“He actually came in with just his hair dyed green and then he got this idea he wanted to cut a shamrock into the side of his head,” said Earls.
“That kind of went a bit pear-shaped and then he was like, ‘let’s get KE 100 into my head’.
“I was sitting in the team room and I was like, I want no part in this and walked away and then Craig (Casey) sent me a picture and what a horrendous job they had done on it.
“That man (Hansen), he’s such a unique character in rugby.
“When you can act like that and cut your hair like that and then go out and perform like that, you just have to leave him be.”