AbilityHeavyweight
As long as there is a Grass Energy attached to Muk, you must pay an additional ColorlessColorless to retreat it.

Muk is Pokédex #089, generation 1 (Kanto). Muk is a Stage 1 Grass Pokémon with 70 HP. The card says it evolves from Grimer. In this catalog that name is Grimer (#088).
Muk sits at 23/147 in Aquapolis, position 23 of 182. Before it is 22 Magneton, and after it is 24 Nidoking. The set belongs to the E-Card series. It was released on January 15, 2003. The printed size is 147. This checklist is longer, at 182 cards. The listed rarity is Rare.
Heavyweight is listed as Poké-Body. As long as there is a Grass Energy attached to Muk, you must pay an additional ColorlessColorless to retreat it. The attack Burning Sludge lists 10 damage. The cost is Colorless, Colorless. Flip a number of coins equal to the amount of Grass Energy attached to Muk. If any of them are heads, the Defending Pokémon is now Poisoned and Burned. Weakness is Psychic ×2. Retreat cost is 1.
Muk (#089) has 31 other cards in the catalog. Those other cards are in 24 sets. The other printings with a release date run from 1999 to 2025. The earliest other card is Muk 13/62 in Fossil (1999). Both list 70 HP. The rarity there is Rare Holo, and here it is Rare. Mitsuhiro Arita illustrated that card, and Hajime Kusajima illustrated this one. Retreat cost there is 2, and here it is 1. 26 other cards of Muk list a different HP.
The illustrator line reads Hajime Kusajima. I count 206 other cards in the catalog with that illustrator.
Aquapolis set binder is where a full Aquapolis set goes. This card fills one slot there. A generation binder holds one card of each species. Muk can fill a slot in Generation 1 binder (Kanto). I still need this card.
As long as there is a Grass Energy attached to Muk, you must pay an additional ColorlessColorless to retreat it.
Flip a number of coins equal to the amount of Grass Energy attached to Muk. If any of them are heads, the Defending Pokémon is now Poisoned and Burned.
Aquapolis, in the E-Card series. It was released on January 15, 2003. The printed size is 147.
23/147. It is entry 23 of 182 in this checklist.
Hajime Kusajima. The catalog lists 206 other cards with that illustrator.
Rare.
Muk #089, generation 1 (Kanto).
Burning Sludge (10).