The arcade version, Um Jammer Lammy NOW!, was made in collaboration with Namco and featured updated visuals and a modified song list. The arcade machine also featured a special guitar controller, and some of the levels were modified to make them easier to play.
The game begins in Lammy's dream. After arriving barely in time for her concert, she discovers that Chop Chop Master Onion has become the new vocalist of her band, MilkCan. His lyrics foreshadow the events of each level in the game, and once it is completed, he points out that Lammy's guitar has transformed into a vacuum cleaner (although she does not seem to recognise it), and then gives a rather nonsensical speech ending with the phrase "Dojo, casino, it's all in the mind".
Lammy then wakes up from her dream and realises that she only has 15 minutes before her concert starts. She begins to rush to her concert but is obstructed by Chief Puddle's fire crew trying to put out a large burning building. As she tries to get past, he notices her and tells her to help put out the fire. Although nervous at first, Lammy notices a billboard for Joe Chin's Casino and remembers Chop Chop Master Onion's speech in her dream, giving her the confidence to put out the fire (as her guitar is "in her mind").
After Lammy puts out the fire, Chief Puddle gives her pizza as thanks, but this causes her stomach to briefly expand. When she remembers her shortly upcoming concert, she again begins to rush but quickly gets tired, and is mistaken by Cathy Piller to be in labour. Once Lammy digests the pizza, Cathy realises her mistake and asks Lammy to help put the delivered babies to sleep. Seeing a few of the babies playing again reminds Lammy of Chop Chop Master Onion's speech, giving her confidence.
Once the babies are asleep, Lammy slips on a skateboard and lands on a low flying plane. The plane's pilot, Captain Fussenpepper, is suffering from rapid personality changes and confusion, and is clearly in no fit state to fly the plane, so Lammy must act as co-pilot. An announcement mentioning the plane's on-board casino reminds her once more of Chop Chop Master Onion's speech, giving her the confidence to fly the plane without crashing.
Unfortunately, Lammy accidentally leaves her guitar on the plane, so she heads into Paul Chuck's shop to buy a new one. He points out how greedy she is being for wanting to give him money in exchange for goods, and so he refuses to make the guitar unless she helps him saw down the wood. Lammy initially protests, as she is running out of time before the concert, but, after overhearing a segment of the song "Casino In My Hair" on the radio, she remembers Chop Chop Master Onion's speech yet again, giving her confidence.
Immediately after getting her new guitar, Lammy slips on a banana peel, dies, and is sent to hell.(Or in NA, Lammy's clothes get caught on the door and flys too far that she time warps on an island). Teriyaki Yoko agrees to bring Lammy back to life for her MilkCan concert as long as she plays well enough as a guitarist in Teriyaki's own performance. Teriyaki hands her a guitar and she is reminded by absolutely nothing at all that her guitar is in her mind (even though her guitar is actually in her hands), giving her the confidence to play for Teriyaki.
Once Teriyaki's performance is over, she sends Lammy back to the living world using what looks like a fax machine, although as Lammy is leaving, she has a brief encounter with her evil twin, Rammy, who is angry that Lammy replaced her in the concert. Once Lammy arrives for her concert, she starts to explain what happened, but so do Ma-san and Katy, indicating that they have been on similarly hectic journeys. Then they play one song at their concert and the game ends.
Parappa, PJ Berri, and Sunny Funny help Katy prepare for the upcoming MilkCan live concert. This inspires both Parappa and PJ to start their own rock band but it falls short, mostly due to PJ's obsession with the güiro.
There are 7 stages in the game. Apart from the main story mode, there are a number of alternate modes, including VS and Team modes (featuring Parappa or Rammy) and the ability to play solo as Parappa. The teacher's lines are modified in Parappa's modes so that he can rap them, but otherwise the songs are identical across modes.
- Stage 1: I Am A Master And You!
- Stage 2: Fire Fire!!
- Stage 3: Baby Baby!!
- Stage 4: Fright Flight!!
- Stage 5: Power Off! Power On!
- Stage 6: Taste Of Teriyaki
- Stage 7: Got To Move!
A large number of religious references were removed from the game when it was brought to the USA. The most infamous of these changes is the replacement of a scene where, originally, Lammy would die and go to hell. This was bowdlerised in the USA release to instead show her being slingshotted to an island. This change allowed this version of the game to receive an E for Everyone rating from the ESRB.
The Stage 6 song itself has some minor differences, with references to the devil and a "mean" angel being removed, and the first level was also changed to replace Chop Chop Master Onion's reference to the level. Stage 5 had "chopping trees down for fun" replaced with "knowing that we're here for the fun".
- Hidden within the audio files for the game is a Parappa version of Stage One's song, which was later used as a new added stage in UmJammer Lammy NOW!. The song is found on the Um Jammer Lammy Original Soundtrack, but the win/fail dialogue of Parappa is only found in the files. You can still hear this dialogue by playing Stage 6 of PaRappa the Rapper and swapping the disc to Um Jammer Lammy.
- Winning COOL mode
Chop Chop: I'm so proud of you. Congratulations.
Parappa: Yeah... by the way; how've you been, teacher?
- Winning COOL mode
- The characters were featured on the Milk Premium Spin-Off, Crystal Hero.
- This is the only game that doesn't have Lessons like Parappa the Rapper 1 & 2.