With wide eyes, Pikachu could do literally nothing as his teammate was trapped in a massive glob of mud. How was an Electric-type like him supposed to get through that!? He had to've known some other, non-Electric-type move, right? Thinking about his options, he remembered one attack.
"Let's hope to Arceus this works..." he murmured to himself, abandoning his spot in front of the stairs in favor of walking up to the Gastrodon, hitting it with a hard Slam.
The Gastrodon reeled back, already almost done for, and tried to hit Pikachu with another Mud Bomb, but it was dodged with a graceful ease. Realizing that it was already beat with no chance of winning, the Water-type refused to continue the battle and made a hasty retreat.
"Too easy," Pikachu scoffed, actually surprised it had been that simple, before turning back to his mud-covered partner. An idea had popped into his mind, and it was the only one he had that could possibly free Destiny. He just hoped he wouldn't hurt her in the process. "Let's try this again." Sucking in a deep breath, he once again used Slam, this time on the mud bubble.
The mud, which had thankfully hardened since being shot, shattered under his weight, sending Pikachu toppling to the ground next to the Eevee. A bit dazed, he flopped onto his back and laughed, looking up to his now-freed partner. "You, uh, alright?" he asked, pausing for more breath while doing so.