Where's Walrus? is a fantastic one.
In Where's Walrus, the zoo is quiet, with no visitors and all the animals (plus the zookeeper) taking afternoon naps. Except for Walrus, who sees the gates open and makes a break.
The zookeeper comes chasing after him, but once outside the gates, can't figure out where Walrus has gone. In each double page spread, Walrus finds a new way to blend in with the people around him, causing the zookeeper great consternation.
I love the retro-looking illustrations and the bold bright colors. Ella lights up every time I pull this one out and we've read it easily once a day since I checked it out from the library.
Children a little older than Ella will probably get a kick out of identifying Walrus in the various photos - he's certainly not hidden like Waldo is. This is definitely aimed for a younger audience.
Scholastic made this fun little video to go along with it:
Copy borrowed from my local library