How to run a menagerie escape?

[Corran]

You may even include some rivals who also deal with the chaos, and are less interested in keeping the rampaging owlbear alive than the characters.

+1 to that.
Arrogant low level npc tries to show off by killing a rampant bull (replace with what you have in stock, I can only think of bulls when imagining the scene however), sticks it with a bolt, animal is in pain, sadistic npc laughs and boasts to their friends and slowly goes to reload the crossbow, bull turns around and runs at them, npc freezes in place. PC(s) watching this have a choice, which you present.They can try to save NPC's (let's call him Duffus); they can try to save Duffus's life (by tackling them out of the way, by stopping the bull at its tracks or drawing its attention or however else they want). Or they can do nothing and let Duffus get killed/injured (up to you, or up to a die). Goes to show how much they value human(oid) life, if they believe that people can change for the better and thus allow them the chance, if anger can get the better of them easily, stuff like that. More importantly, you can make something out of it by having Duffus's pa or ma be a person of importance, so what the pc's do in that situation may provide them some minor benefits or hindrances in the near distant future (let enough time pass before you use it; some NPC they'll one day need to convince about something can be the parent, so their decisions during that day could influence their efforts).

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The real question though? Who caused this mayhem and why?

A) Light hearted option. Two kids in love. Their respective families own two competing menageries and hold a grudge against each other. Kids created the situation so they could escape within the chaos and go and get married in that small temple at the outskirts of the city (been arranged). Each one left a note to their parents. Split the group up in all the chaos (just have multiple bad stuff going on in different directions so the only way they can handle them is if they split up in two groups or more). Each family apporaches half of the party, explaining the situation. Throw in accusations of witchcraft, of kidnapping, whatever might make your players bite, so that they'll not totally expect a small peacefull wedding ceremony when/if they get to the chapel in time. Heck, have the poor wizard absent pc be there as a witness. He just visited the temple for some herbs/potions for that food poisoning, couple couldn't get married without a witness, so they kind of convinced him to stay put and witness the ceremony. If pc's are keen on letting the ceremony proceed, have an angry crowd (the families) arrive outside the temple. Bards will probably negotiate and/or stall to win time, fighters might block the door and lift a few npcs up in the air or something, or handle it in whatever other way they see fit and hopefully surprise you.

B) Murder! Someone caused chaos to get away with it. Plenty of blood, but no body around (to bring back or to ask questions of). No one saw a body moved, and zone of truth (let the pcs earn this opportunity) reveals nothing if cast on anyone from the menageries. Who did it? Where is the body? And why the single clue found in the scene of the supposed crime points to the poor food poisoned wizard pc who is clearly ill and could not have done it (neither did he do it)?

C) Old good thievery. The mayhem kept the city guard busy for several hours, and now, about one hour later and a couple of guards knoced unconscious, the baroness's prized diamond is stolen! What a heist! This is not a task for high level pcs. Humor them. Have them first hear about it by overhearing another adventuring group (low level party) who are investigating. Probably asking your pcs for some help or tips. The diamond was stolen by a member of the baroness's kitchen stuff. Wants to use it to bring back to life his recently deceased daughter. He had nothing to do with the wild animals going free. That was just Tymora smiling on him a little. Might be hard to keep your pcs invested so they can reach the simple dilemma at the end (without completelly bypassing the obstacles with magic), so this may only be worth it if you can make the newbies entertaining enough for your pcs to stick around a little and letting them try to figure this out. Cheap but effective, make each newbie npc resemble t least a little each ones of your pcs, and plan at least for one roleplaying scene for every pairing (think of advice the npc might ask of the pc and plan for one or two interesting questions). If they get along, then for added drama you could have the newbie npcs stand on the opposite side of your pcs when it comes to the end dilemma.