His stage name, owing to his gambling hobby, is derived from the phrase kääriä rahaa, "make a fast buck".

[10] On 11 January 2023, Pöyhönen was announced as one of seven participants in Uuden Musiikin Kilpailu 2023, the Finnish national selection for the Eurovision Song Contest 2023.

[14] Ahead of Eurovision, Finnish software company Zoan created an experience inside the popular online video game Fortnite, where players can visit a virtual rendering of Helsinki's Senate Square with Käärijä signs and stages.

[23][24] On social media Pöyhönen uses the name "Paidaton Riehuja", which translates to "shirtless rampager", and is a reference to his punk rap song of the same title.

[26] Sometimes, a yellow-clad doppelgänger on rollerblades called "Häärijä" (or "Paidaton Kiehuja" on social media), who's real name is Tomi Häppölä, has been observed in connection with Käärijä.

Pöyhönen has spoken about suffering from ulcerative colitis since his teenage years, culminating in emergency intestine removal surgery in 2014.