As Promised, The Crab
As you can see, someone (Johanna, presumably) really wants to get her pet crab Oliver back. There's even a ten dollar reward. Now, you might be compelled to think that this is a fake, or a joke of some kind, but why would the person put not only their email address, but their phone number on the sign? You'd think that would be a rather daring invitation for every weirdo out there to harass you, and maybe even insist on bringing you a crab. Hmm. Maybe one of Johanna's enemies put up this sign...
That's Not A Cat, Dan
Hilarious. Notice how the “Fe-” was added above “male”, indicating that the gender wasn't initially known, but was certainly confirmed at some point.
The Unhappy Chicken
This sign is almost certainly legit. Some silly do-gooder found a chicken outside a Chinese restaurant (no doubt why the chicken looked unhappy in the first place) and thought it was someone's pet, instead of a teriyaki side dish.
“Answers to Huck”
Yes, this image has been around since before the movie Ted.
Tears of the Unicorn
All of the unicorns are missing. :(
“Likes Deviled Eggs”
The real question here is how in god's name could a bizarre abomination like that ever go missing. How could you even have trouble finding something so uniquely recognizable? Is it a llama? Either way, it likes deviled eggs, responds to Dexter, and without a doubt really must be the best pet ever.