Can I get Double Fusion Tokens without Robux?

Yes! Rare rewards in high-tier zones of The Wild can award Fusion Tokens upon clearing combat chambers.

Do Game Passes apply across all game sessions?

Yes. Both 2x Money and 2x Egg Growth Speed are permanent, one-time account purchases tied to your Roblox profile.

No. The upgrade panel shows $5K on the in-game cash button with a 19 Robux button beside it, so both routes are on the same screen.

You do not need Robux to progress smoothly in Impossible Animals. The two most critical progression systems feature purely in-game cash pricing:

Jade Charm (x2 Levels While Training): Costs only $5,000 ($5K) in-game cash at the upgrade stall. This permanently doubles your treadmill XP gain speed without spending any Robux.
Pen Expansions: Read straight off the pen sign: Level 3 (6 slots) costs $100K, Level 4 (7 slots) costs $2.5M, Level 5 (8 slots) costs $60M. Each step adds exactly one slot.
Treadmill Upgrades: The treadmill sign shows both the XP rate and the price: Level 4 (60 XP/s) costs $5M, and the step after it costs $1B.
Base Parent Unlocks: All base parents are unlocked for free by defeating combat zones in The Wild.

For players looking to accelerate their progression, the official game store offers two permanent Game Passes:

2x Money (Pass ID 1979348991): 399 Robux. Permanently doubles all idle $/s cash produced by hybrids roaming in your pen. Essential for rapid multi-million tycoon expansion.
2x Egg Growth Speed (Pass ID 1978617271): 467 Robux. Permanently cuts egg incubation timers in half (Common Eggs hatch in 10s instead of 20s; Epic Eggs hatch in 45s instead of 90s).

Developer Products are repeatable consumable purchases cataloged on the official Roblox API:

Double-Fusion Tokens (4 tiers): 1 Token (80 R$), 3 Tokens (200 R$), 10 Tokens (640 R$), 50 Tokens (2,800 R$). Note: Tokens can also be earned as rare drops in The Wild.
Instant Hatch (6 tiers): Common Egg instant hatch observed at 7 Robux in gameplay screens (up to 4+ hours at 129 R$).
Charms (9 tiers): Jade (19 R$), Arcane (29 R$), Gilded (49 R$), Diamond (79 R$), Radioactive (119 R$), Chaos (199 R$), Celestial (349 R$), Iridescent (599 R$), Divine (999 R$). (Remember: Jade Charm can also be bought for $5K in-game cash!)
Treadmill Level Packs (9 tiers): Level 2 (19 R$) up to Level 10 (1,299 R$).
Level Multipliers (12 tiers): 2x (3 R$) up to 4096x Levels Multiplier (1,375 R$).
Cash Packs (5 tiers): +$24,000 (40 R$) up to +$8,000,000 (640 R$).
Egg Packs (4 tiers): 1 Egg (80 R$) up to 50 Eggs (2,800 R$).

Compare a cash pack against your pen rate first: a 10★ Stegosawasp recorded at $410/s produces roughly $1.47M per hour. Whether a pack is worth buying depends on how far your pen is from that rate, so check your own pen income before spending.
Buy Jade Charm with In-Game Cash: Always use $5K in-game cash to buy the Jade Charm instead of paying 19 Robux.
Confirm Prompts: Always verify the Robux amount in the native Roblox confirmation modal before completing any transaction.