By utilizing paralysis and Iron Head's boosted flinch rate thanks to Serene Grace, Jirachi can ensure that his opponents will only ever have a 30% chance of successfully attacking with a 100% accurate move. This set takes full advantage of these odds by providing Jirachi with the ability to heal 6.25% of his health for free with Leftovers every time his opponent gets flinched or is fully paralyzed. Substitute allows Jirachi to safely attempt to flinch opponents who would otherwise OHKO him. With Leftovers, Jirachi fully regains all his health lost from Substitute after successfully preventing his opponent from attacking four times. At this point, Jirachi has likely done significant damage, and is now back to full health.
Unlike most other sets, this set should be played with long-term planning in mind. In other words, it often takes two switch-ins from this Jirachi to be as successful as possible. The first time Jirachi comes in, he should paralyze his opponent's counter, and then switch out. The next time Jirachi finds an opening to come in, he should use Substitute while his opponent switches back to the same paralyzed counter, and then begin to wreck havoc. Of course, Jirachi could attempt to keep using Substitute the first time he comes out until his opponent is fully paralyzed, but that is not the most reliable strategy.
176 Speed EVs and a Jolly nature allow Jirachi to outpace all positive nature base 90 Speed Pokemon, most notably Lucario. 168 Attack EVs allow Jirachi to then OHKO Lucario after Life Orb recoil and a Defense drop. Even without max Attack, this spread still allows Jirachi to get the OHKOs and 2HKOs that he would get with 252 EVs. The rest are thrown into HP and give Jirachi a nice amount of bulk to round out the set; however, if you want even more bulk, a 252 HP / 220 Atk / 36 Spe spread works too. The 252 HP EVs give Jirachi 101 HP Substitutes that aren't broken by Seismic Toss. For that spread, a Careful, Impish, or Adamant nature will work, and really depends on what you need. Careful allows Jirachi to take attacks from Starmie and other special attackers more easily. Impish does the same, except for physical attackers like Machamp. Adamant will give Jirachi a nice boost in Attack. Since Jirachi should be paralyzing most switch-ins, max Speed is generally not needed, making this secondary spread just as viable as the original. If you want to maximize Jirachi's offensive power, you may also use 80 HP / 252 Atk / 176 Spe with a Jolly nature.
Body Slam may be considered over Thunder Wave, as it allows Jirachi to paralyze Pokemon immune to Electric-type attacks, such as Swampert, Gliscor, Flygon, Hippowdon, Jolteon, and Electivire. It also provides Jirachi with a form of neutral damage versus Water-type Pokemon, who otherwise resist all of Jirachi's attacks. It is generally an inferior option to Thunder Wave though, as Body Slam only has a 60% chance to paralyze, and does not affect Ghost-type Pokemon.
Although this set is incredibly difficult for people to play around, it does have some hard counters. Pokemon who are immune to Thunder Wave or resist Iron Head and Fire Punch usually fit the bill. Such Pokemon are Hippowdon, Swampert, Gliscor, and Flygon. They each are immune to Thunder Wave, take little from Iron Head, and can hit back with powerful Ground-type attacks. Starmie is also a good counter because he resists Jirachi's attacks, and even though Jirachi can paralyze him, Starmie can easily switch out, ridding himself of paralysis thanks to Natural Cure. Suicune also resists Jirachi's attacks, can set up Calm Minds, and use Rest to rid itself of paralysis. Heatran is a decent counter as well; Jirachi is able to paralyze him, but he still takes very little from Jirachi's attacks, and can hit hard with his STAB Fire-type attacks. Jolteon is also a good check because he is immune to Thunder Wave, resists Iron Head, and can break through Jirachi's Substitutes with STAB Thunderbolt without worrying about being flinched.
Because Jirachi should be behind a Substitute most of the time, the opponent will be eager to break it. That makes any Pokemon who resists Fire- and Ground-type attacks a solid partner with Jirachi. Salamence and Gyarados are both excellent choices. Mixed Salamence can switch in on either of those, and use moves like Draco Meteor to force out bulky Ground- and Water-types. Gyarados loves getting free switch-ins so he can set up with Dragon Dance. His STAB Water-type attacks can also scare off the Ground-types who hinder Jirachi. Jirachi will also appreciate a Heatran with Toxic on his team. Heatran is a great lure for the same Pokemon, like Swampert and Vaporeon, who stop Jirachi. Toxic will make them essentially useless when facing Jirachi. Specially Defensive Skarmory walls Pokemon like Hippowdon and Vaporeon and appreciates the extra turns to set up Spikes. Any Pokemon who benefit from a paralyzed opponent, like Machamp and Salamence, will work great with this set too.
