Here’s a short guide to the “Peter’s Dream” game mode. If any information here is incorrect, please let me know in the comments.

Spoilers for all unlockable Peters!

Last Updated: Jul. 3 2024 (game v1.0.18)

“Peter’s Dream” is unlocked after completing Story Mode for the first time. Level of completion does not appear to affect if the mode is unlocked.

During this game mode, the player Peter(s) must fight against endless waves of enemy Peters. Each wave spawns immediately after the final enemy Peter is defeated in the last one. There are a set number of enemy Peter configurations, which loop continuously once the cycle has completed. Note that Wave 1 ("Doppelganger") is excluded from the rotation after its first appearance. The arena scrolls, and continuously loops between an arrangement of platform and hazard setups. This continues for as long as the player(s) can survive!

Blue orbs are scattered along the top half of the arena, scrolling along with the stage. Coming into contact with these orbs allows the player Peter to change his form in accordance with the Peter image it currently displays. The available forms at any given time seem to be chosen randomly. Peter forms that were not previously unlocked by the player in story mode appear, and can(?) be selected. After an orb is “used,” it will become unusable for a few moments before refreshing.

Touching these blue orbs additionally restores a small amount of HP to the player Peter’s health bar. This health restoration refreshes when the orb refreshes.

A special enemy, NIGHTMARE, appears every 10 waves.

This game mode is one all about endurance. While attacking enemies is important, being able to put distance between yourself and them is equally key. Just like in Story Mode, enemy Peters can also attack one another, so sometimes it will be safer to hang on the sidelines and let them deal with each other.

Staying in the same Peter form for a long period of time is not recommended for survivability.
The first few waves can quickly be dealt with with Peter Shorts' headbutt. After you begin to take damage, swap Peter forms regularly to continually keep your HP as close to full as possible, in case something really goes awry. Swapping forms at every opportunity might not be ideal, instead keep an eye out for Peter forms you are familiar and confident in using.

Try to avoid swapping to Peters with lower vertical mobility (Tiger Peter, Snail Peter, Mecha Peter, etc.) because it can make reaching blue orbs, on top of fighting off enemies, difficult. Conversely, Peters with higher air maneuverability (Bird Peter, Peter Pants, Pepeller, Pteterodactyl, etc.) can prove quite useful for quick swaps and fast recovery.

The NIGHTMARE “boss” fights may initially be the most challenging part of this game mode. As an enemy, it actually only takes a couple of hits to defeat. However it constantly moves around the player in circles, making it difficult to land a direct or projectile hit on.

Pay attention to how many waves you've cleared, and try to be towards the center of the arena when the Nightmare spawns in to avoid getting cornered. In my experience, the most reliable method is to use a side attack (L/R + B) while airborne when it gets close. Fire Peter and Peter Pants have been my most reliable choices for this endeavor. There is a certain rhythm to it that takes a little practice. If you take damage, you do have wiggle room to recuperate by collecting any blue orbs that pass by. Stay away from the edges, keep trying and you should land a hit eventually - just take it slow and steady!

A total of 49 enemies appear in a single "loop," 48 after the initial loop.
For the "Lucid Petering" achievement, You must survive until Wave 41, approximately.

1. Doppelganger

• Peter x1

2. Beter's Revenge

• Baby Peter x2
  
• Mecha Peter x1

3. Fire n' Ice

• Fire Peter x1
  
• Ice Peter x1

4. Thunderstorm

• Elec Peter x1
• Wind Peter x1

5. Flight of the Peter

• Bird Peter x1
• Bat Peter x1
• Propeller Peter x1
• Dragon Peter x1

6. Secret Friends

• Bird Peter x1
• Peter Pants x1
• Moai Peter x1

7. Life's A Jungle

• Tigeter x1
• Frog Peter x1
• Beetle Peter x1

8. Meme Team

• Moai Peter x1
• Tigeter x1
• Alpaca Peter x1

9. Peetledee and Peetledum

• Fat Peter x2

10. NIGHTMARE

11. Cold-Blooded Killers

• Ice Peter x1
• Lizard Peter x1
• Dragon Peter x1

12. Peter & the Parable

• Sneeter x1
• Rabbit Peter x1

13. Peter's Flying Circus

• Propeller Peter x1
• Rabbit Peter x1
• Tigeter x1

14. The Brothers Pete

• Peter Shirts x1
• Fat Peter x1

15. Fire Types

• Fire Peter x1
• Lizard Peter x1
• Dragon Peter x1

16. Ice Types

• Ice Peter x1
• Peter-O-Dactyl x1
• Peterguin x1

17. Fossil Friends

• Sneeter x1
• Dragon Peter x1
• Peter-O-Dactyl x1

18. Easter Petes

• Bird Peter x1
• Moai Peter x1
• Rabbit Peter x1

19. Kings of Peter

• Peter Pants x1
• Sigma Peter x1

20. NIGHTMARE

Waves repeat indefinitely past this point, excluding Wave 1.

Thanks for reading, and happy Petering!