Ash caught a Snorlax because of Jigglypuff's Sing, this happens in episode 96 Snack Attack.
Known Moves
Ash's Snorlax (Japanese: サトシのカビゴン Satoshi's Kabigon) was the second Pokémon caught by Ash Ketchum in the Orange Islands. Its Japanese voice actor is Katsuyuki Konishi. Its English voice actors are Michael Haigney (4Kids and PUSA with stock footage), and Eric Stuart (The Garden of Eatin', Showndown in the Oak Corral and The Right Place and the Right Mime).
Rest, Body Slam, Mega Kick, Mega Punch, Hyper Beam, Ice Punch, Tackle, Protect, and Headbutt.
History Orange Archipelago
During his travels in the Orange Islands in Snack Attack, Ash discovered a grapefruit orchard that was under attack by a Snorlax that was eating everything in sight, and was consuming many of the nearby islands vegetation within days. Ash, Misty, Tracey, Pikachu and Jigglypuff eventually managed to stop the Snorlax. This gave Ash the perfect opportunity to catch it.
Ash kept the Snorlax on his team for the remainder of his time in the Orange Islands, but could not use it in the finals due to the fact that it would not wake up and needed to be switched with one of Ash's thirty Tauros. After the tournament was won, Ash then decided to keep his Snorlax at []Professor Oak's]] permanently because he could no longer feed it and only called upon its power in major battles.
Johto
Since then, Snorlax has become one of the senior members of Ash's team, along with Charizard and Pikachu and has provided much needed comic relief in many situations. Ash called upon it for the Sumo Conference in Ring Masters, winning the subsequent fight as a result, and later used it to defeat Clair's Kingdra in their rematch. He also used Snorlax during the Johto League competition, first against Gary Oak where it quickly defeated Gary's Nidoqueen andArcanine, but lost to Scizor. Snorlax then fought during Ash's following match against Harrison, defeating his Steelix andHypno, though in the end it fell to his Houndoom.
Kanto Battle Frontier
When Ash returned from Hoenn, with May and Max, Snorlax befriended May's Munchlax. Most recently, Snorlax helped Ash earn the Guts Symbol from Greta in Wheel of Frontier by defeating her Hariyama with an Ice Punch and literally flattening her Medicham with Body Slam.
Sinnoh
It appeared in DP182 alongside Ash's other Pokémon. It was not in its Poké Ball, like many of Ash's other Pokémon, and was found in the kitchen, eating restaurant food. It was later used in the battle against Team Rocket, but it was sleeping. Ash tried to wake up Snorlax, but it accidentally rolled over, tipping the Team Rocket Mecha over. It was seen again in DP184 where it defeated a trainer's Grumpig with a powerful Body Slam, helping Ash progress to the third round.