The Australian prop celebrated his 200th game for the club by scoring a 78th converted try that took Friday’s fixture against Huddersfield Giants into Golden Point extra-time.
Pete Mata’utia then stepped up with the crucial drop-goal to snatch the victory at Wheldon Road.
Millington, 32, said: “I’ll definitely remember that one.
“I’ve just been saying how my 250th career appearance was down here against Wigan when we had that comeback.
“So my 250th career match and this 200th Cas game have both been pretty special.
“It was great to dig that win out like we did and I’ll certainly remember both.”
Tigers were 20-0 down when they came back to beat Wigan 38-28 in April and there was famous scenes as well on Friday.
Millington, one of Super League’s top value overseas signings since joining from Canterbury Bulldogs in 2012, popped up at just the right time to latch onto fellow prop Daniel Smith’s unlikely grubber after Jordan Turner failed to clear.
“It just happened didn’t it?” he recollected, just as Castleford looked destined for a sixth defeat in seven games.
“I noticed (Darnell) McIntosh in the line and it wasn’t the most conventional kicker in Smithy there.
“But he’s knocked one through and it’s paid off.
“It's one of those that’s very reactive and he’s a good rugby player is Smithy. “He’s done well there to put it through like that.
“It was a nice one to lock it up but there was still plenty to be done.”
“Huddersfield are a tough side. They defend really well, they are such a hard-working team and they are really hard to break and down and they are doing a really good job.
“We knew it’d be a good battle. It probably wasn’t the prettiest rugby match to watch but I think the ending gave the fans enough to cheer about.”
There was chaotic scenes in extra-time with spilled ball from both sides, Castleford’s Jake Trueman and Jordan Rankin both missing with drop goal attempts and Huddersfield even trying one from halfway.
“I wanted it as well!” joked Millington, as Tigers moved up to fifth ahead of Thursday’s visit from Hull FC.
“It’s just one of those things what happened out there.
“A few of the lads had a crack and then Pete put his hand up and he nailed it. “It’s just great to see guys with plenty of confidence as that's what you need. “We've not been playing our greatest and have been scrapping for wins at times.
“But when you start getting that confidence coming back through your side that's when you start playing good rugby.
“Hopefully we can build on this. We’ve another couple of tough ones coming up but hopefully we can get back towards what we know we can playing-wise.”