I'm so glad somebody else ships Penny and Sherman! Their dynamic has so much untapped potential for adventure, way more than just classroom scenes. Most fics lean into the 'awkward crush' angle, which is cute, but I get a bigger kick out of stories that throw them into a crisis together. One I keep rereading is 'Signal Lost' on AO3, where a school trip to the natural history museum goes sideways—think power outage, escaped exhibit specimens, the whole deal. It's them navigating dark halls, Sherman using his encyclopedic knowledge to identify threats, and Penny's practical, stubborn bravery keeping them moving.
It's not just about danger, though. The teamwork comes from them compensating for each other's weaknesses. Sherman overthinking a plan while Penny just grabs his hand and says 'Run now, think later.' That friction turning into a solid rhythm is the core of it for me. I've seen a few crossovers too, like a 'Stranger Things' AU where they're the party members stuck in the Upside Down, which hits that same note of relying on each other in a weird, hostile environment.
Honestly, the best adventure fics for them feel like a modern-day 'Goonies' but with more brainy banter.