You know what? Omake time, because the Pengrenade idea wouldn't leave me alone.
Charge of the Pengrenade
The Egg Brain was hard at work for its master, refining his failed designs and iterating on his successes, as usual. Its latest project was simplifying E-102 Gamma's design to facilitate mass production; it was considering a change in the naming scheme to differentiate them from their prototype, but such concerns were premature before it had a functional blueprint that matched its goal.
These new, mass-produced E-Series machines would likely fulfill a role roughly equivalent to a squad captain, but they would not design themselves, no matter how many temporal shenanigans were involved.
Nevertheless, the Brain, like its creator, was not without its whims, and inspiration is a fickle beast; so it was that, in a moment of distraction, it prototyped a very different machine to deploy under the command of its second original design.
Taking cues from some of the doctor's older designs, such as the Grabber or Jellygnite, its primary attack would be an explosive charge. However, unlike those designs, its detonation trigger would be the destruction of the body, rather than a manually-triggered self-destruct sequence upon capturing its prey; after all, multiple after-action reviews included Sonic or Tails managing to squirm free of their grasp during the countdown (which likely explained why those designs had been decommissioned).
Naturally, an animal core would be wasted in a design built on the assumption that it would be destroyed in battle, so it was instead given an AI based on the Egg Pawns; quirky as it was, it was still the best cost-effective processor available.
Updated Buzz Bomber engines along the base, combined with retractable sled tracks on the front, would give it sufficient pursuit speed that their targets would be hard-pressed to outrun them with anything short of a Super Form, and deactivating one side's engines would greatly facilitate turning as well.
If it was going to charge its targets anyway, a spiked ram mounted on the most likely point of contact was only reasonable.
Only a minimum of frame reinforcement was done; these were meant to be destroyed, after all, so not being destroyed in a single hit would be counterproductive.
Might as well give them speech capability, to facilitate reports should one manage to survive long enough. Or to taunt the doctor's enemies, should the mood take them.
If they're going to work for a polar bear, might as well model them after a penguin; sure, there was already a penguin-based design, but redundancy never stopped the doctor, so that was considered irrelevant.
After a brief testing period to ensure these Pengrenades detonated when desired (and ONLY when desired), it submitted the design as a "potentially-useful byproduct" and, whim appeased, turned its attention back to its true project.
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Knuckles stomped towards Eggman's arctic base; he had heard that an Emerald- the fox wasn't too clear on whether it was a Chaos Emerald or a fragment of the Master Emerald- was being kept here, and he needed to retrieve it.
"Intruder spotted, dood!" a high-pitched voice abruptly yelled, calling his attention to... a robot penguin wearing a spiked helmet? "Moving to engage, dood!" it added as it dove forward, boosters igniting on the bottom as it started sliding towards him at high speed.
"Hmph, is this it?" Knuckles scoffed before jumping over the spikes and crashing down on its back fist-first.
He was sure this would destroy the flimsy-looking bird; however, he wasn't expecting that to make it explode with enough force to blast him into a nearby snowbank.
He took a moment to shake his head to clear it, only to see more of those penguins sliding towards him. "You gotta be kidding me..." he muttered.