These have all been great. I think my goofiest moments have been in table top sessions too. Here are two of my favorites. Spoilers ahead for Lost mines of Phandelver... sorta I guess? Who cares.
During a game of Lost Mines of Phandelver, we had a kid playing. Your typical squeaker, but really respectful and nice. He was playing a halfling rogue who had a backstory involving the red brands. We of course, end up sneaking our way into the red brand's hideout but we eventually get caught.
We are all failing to hide or preparing to fight but then, the kid speaks up quickly.
"It's Glass Staff's birthday."
The bandits pause, and he has to roll a deception check that he succeeds with flying colors.
We end up convincing these guys to go out and buy some gifts with us and help us throw a surprise party for the glass staff, where we get the drop on him and knock the wizard out turn one. It was legendary.
My other story is for a Starfinder game I was running. The group was helping a frog species liberate itself. Part of their mission was to destroy a massive oil drilling operation. Thus ensued a very spy movie esque plan to sneak it, during which the party subdued a gaurd and one of the players disguised themself as him.
They proceeded to use this disguise to get to the security room to shut off the Cameras. They get a couple fails on small lies and persuasion checks and one of the gaurds gets suspicion. He says that the person being impersonated never leaves their post and a little lapse in judgment in my mind ended with me saying, "he doesn't even take bathroom breaks, I've seen it".
The player obviously leaps on that, using it to shift the conversation away from them. Ended up buying time for the rest of the party to get past the cameras.