People stunned to find out The Penguin star Cristin Milioti had a role in The Sopranos

The Penguin fans have worked out where they've seen one of the lead actors before.

I'm not sure about you, but I'm the type of person who will sit through the duration of a movie or TV series racking my brain about where I've seen an actor previously (before Googling it, of course).

And it seems as if The Penguin viewers have experienced something similar of late in regards to Cristini Milioti - who stars as an impeccable Sofia Falcone in the HBO show.

Many people might recognize Milioti from How I Met Your Mother where (spoiler alert) she's revealed as The Mother referred to in the sit-com title.

However, it's an older TV show that people have worked out that she starred in as it has some resemblance to her Italian gangster character of Falcone.

Worked it out yet? Yep. Milioti also starred in The Sopranos.

Cristin Milioti plays Sofia Falcone in The Penguin (Jon Kopaloff/Getty Images)

She portrayed Catherine Sacrimoni, the younger daughter of John Sacrimoni (Vincent Curatola).

Taking to Facebook to point this out, one person wrote alongside a snap of Milioti as Falcone: "The fact that she's played by Johnny Sack's daughter makes it even better. 'And that kidsh, is How I Met your Mudda'."

"I totally forgot about that," one person replied to the post, while a second said: "Knew I'd seen her somewhere before!!!"

Elsewhere, people went on to rave about other roles that Milioti's had; one being as Jordan Belford's first wife in Wolf of Wall Street.

She has also starred in Palm Springs alongside Andy Samberg, The Mindy Project, Black Mirror and Prime Video series, Modern Love.

While many were quick to recognize Milioti in The Penguin, others may have struggled to notice Colin Farrell underneath the masses of prosthetics he used for this role as Oz Cobb.

Colin Farrell is unrecognizable as Oz Cobb in The Penguin (HBO)

While he wasn't a huge fan having to sit in the make up chair for three hours each day, physically transforming into The Penguin himself wasn't an option for the Golden Globe-winning actor.

Speaking to UNILAD, Farrell revealed: "I'd just come of filming something called The North Water and I'd put on a good bit of weight of that.

"For me it was an enormous amount of weight and when I met Matt Reeves for The Batman film, he took one look at my body and said, 'I love the way you look. I love the shape of your body,' and I said, 'Well say goodbye to it because I have gout and I have to get healthy.'"

He added that he was 'all about losing the weight' and even tried to pitch the idea of a skinny Oz Cobb to Reeves.

Farrell further shared: "I tried to pitch [Reeves] the idea of a skinny Penguin - which he wasn't buying at all. Thank god for technology and the terrific people that designed the bodysuit so I didn't have to [put more weight on]."

The Penguin is available to watch on Sky and streaming service NOW, with new episodes out every Monday in the UK. The series is available to stream on HBO and Max in the US, with new episodes dropping every Sunday.