With the later addition of Finn’s neighbour Chris Garland on lead guitar and Selwyn College schoolmate Joe Bramley on bass, the group formed the band Lazy Boy. In September 1999, Lazy Boy played their first show as a full band at Auckland’s Galatos venue. Citing the possibility of legal action from the global reclining chair company of the same name, the band changed their name; but not before releasing the single 'Brighter Sound’ which appeared on the soundtrack of the Australian movie Cut. (The track later featured on Betchadupa’s The 3D EP.)

In need of a new title, the group lifted the text from a T-shirt that declared: "You Betchadupa I'm Polish" — "dupa" meaning "arse" in Polish. The name was also alleged to come from the top line of an eye chart that Liam once had to read. 

The betchadupa EP was released in January 2001 through Flying Nun.

Further songs written during school holidays would later form Betchadupa’s debut EP. Recorded and mixed by Sam Gibson, the self-titled EP contained six songs including the singles ‘Spill The Light’ and ‘Empty Head’, both of which gained a healthy amount of play on mainstream radio. ‘Empty Head’ entered the New Zealand Top 40 Singles Chart for two weeks and was nominated for the 2000 APRA Silver Scroll Award (the eventual winner was Chris Knox’s ‘My Only Friend’).

The betchadupa EP was released in January 2001 through the iconic New Zealand label Flying Nun Records. The connection was established while the band were still at high school and lasted for the release of two EPs and one album, before being severed in 2003.

“At the time Flying Nun were the only label who were happy to let us do what we wanted to do, which was record one EP at a time and build it up slowly” Liam Finn told the Otago Daily Times in February 2001.

While the band’s promotion was initially aided by their famous connections, they soon grew tired of media comparing them to their parents’ achievements.

Liam Finn told Pavement magazine in February 2002: “If we’re going to get somewhere we want to get there on our own merits and because of the music. People are always going to compare me to him and say that we only got to where we are ‘cos I’m Neil Finn’s son. But we went through the same shit everyone else went through. We had to pay our dues. We don’t get any star treatment and we don’t expect it.”

After finishing high school, the band released their second EP via Flying Nun. The 3D EP built on the band’s melodic pop-rock sound and proved more successful than their debut, gaining them the title of Top New Act at the 2001 NZ Music Awards and a nomination for Best Rock Release at the bNet NZ Music Awards. The New Zealand release was accompanied by a pair of 3D glasses. The single ‘Man On My Left’ was released in Australia through Sputnik Records.

As a result of their well-honed live show and blossoming profile, the band was offered support slots alongside international bands Queens of the Stone Age, Foo Fighters and Jane's Addiction. They ended 2001 by featuring in Neil Finn’s five-night concert series 7 Worlds Collide at Auckland's St James Theatre, where they performed versions of the Split Enz classics ‘History Never Repeats’ and ‘I See Red’ alongside Pearl Jam’s Eddie Vedder and Tim Finn.

The band’s debut album remained in the charts for three weeks, peaking at No.2.

The band’s debut album The Alphabetchadupa was released in 2002 and remained in the charts for three weeks, peaking at No.2. Intending to emulate their energetic live sound on record, the band opted to continue with the straightforward format of two guitars, bass and drums, with a limited number of overdubs.

Finn told NZ Musician in October/November 2004: "I think honesty is the word that probably sums up what we're trying to achieve. Playing live and making music that is honest. We're not trying to be anything we're not and we're not trying to fool anyone. We're just trying to show people how much of a good time it is."

Having spent the majority of the year across the ditch in Australia, the four-piece decided to base themselves in Melbourne, intending to focus on the Australian market. The band gained label help from Australian imprint Liberation Music, part of Michael Gudinski's Mushroom Group.

Finn continues: "I think Liberation came along at the right time and said the right things. They seemed to know what we were trying to do and the plan they had for what we're doing was a lot more realistic."

After being invited to perform at the influential South By Southwest festival (SXSW) in Austin, Texas, they also secured management from American company Spivak Sobol Entertainment and local management from Dave Benge (Fur Patrol, Cassette).

"I guess he's our manager but he's just helping out [until] we get our feet on the ground and maybe that'll turn into Australia/New Zealand management."

Amid a jam-packed touring schedule, the band enlisted producer Nick Launay (Midnight Oil, Silverchair, Nick Cave), to record their second album. Launay was originally roped in to mix the single ‘Sleepy News’ on their first album and told the band he'd like to produce an album. Two weeks were spent tracking the album at the Milk Bar Studio in Sydney, followed by another two weeks adding extra parts at Neil Finn's Auckland studio (Roundhead), at the time referred to as "The Building".

"This album is probably a lot more focused in a way. The last one, like the EPs, could have been a few different bands and different songs and this album is as equally as diverse but I think it definitely sounds like one band playing them all," said Finn.

Aiming for Your Head was released in Australia on 20 September, 2004 and in NZ on 4 October.

However, after 11 months of living and touring in Australia, the band decided to pack up and try their luck in the UK.

In Real Groove magazine, in June 2006, Finn said, “We were going really well and had got a similar point to where we were at in New Zealand. We were a medium level band, above many bands, but it would have taken us another year or two years to crank it up another level, to the top level where you can start selling records, you can tour and you can make money. We figured instead of waiting another couple of years we might as well use that time to come over here or America. We decided that the UK was a better place for our music because they’re more accepting of music here that’s a bit left of centre. American commercial radio and its charts are so middle of the road that we wouldn’t have a hope really.”

In between playing regular gigs, they released a 7" single, a double A-side of ‘Coming Through the Window’ and ‘The Bats of Darkwell Lane’ from Aiming For Your Head, through English boutique label Izumi Records. Work had also begun on a third album.

“We’ve recorded lots of stuff that we’re really happy with. It’s hard to know what sort of direction we want to go down, it’s hard to know what we want to release next.”

Eighteen months after the migration, the band decided to go on an indefinite hiatus.

In between playing as part of the reformed Crowded House live line-up, Liam began work on a solo album, initially under the moniker Lester Osbourne. He eventually released the album, his debut, I’ll Be Lightning, under his own name in 2007 to critical acclaim. Finn's live band, The Dream Team, has on occasion included Matt Eccles. Eccles spent a stint behind the kit as part of Tim Finn's touring band before joining Belgian indie band Das Pop.

The band reunited for a one-off gig at Auckland’s Whammy Bar in January 2008. It is uncertain whether they will ever reform again.