A few years ago we had a cozy little gang that got together every other week. As such, we often forgot what had happened in previous sessions. In one of our adventures, the rogue found a Bag of Holding and proceeded to stuff a live alligator inside.
Cut to a few weeks later, during a boss fight:
DM: It’s looking bad. 12 damage to the paladin.
Rogue: I know it’s my turn, hold on, there’s got to be something I can use -
Cleric: The alligator! Unleash the alligator!
Rogue: Oh my god. I do it. I open my Bag and release the alligator.
Table, chanting: Alligator! Alligator! Alligator!
DM: …. a bloated, slimy, alligator corpse slips out onto the dungeon floor. I hope you’re happy.
Rogue: It’s dead???
DM: You kept it in a bag for weeks with no food or water, what did you expect?