This show is absolutely wonderful. It was the first show we felt good about sharing with our 2.5-year-old a couple of years ago. He'd still love watching it, except now we've seen all the episodes! I can't say enough good things about it. The teamwork elements are excellent. The animals are in just the right amount of "peril" (ranging from a dolphin stuck in a net to a puppy who needs to figure out how to use the doggie door). The music is fantastic -- each episode's music is played by a studio orchestra. The dialogue and song lyrics are adorable, witty, and enjoyed by all of us. The structure of the episodes is excellent -- there's a clear pattern to each story, and sometimes deliberate breaks from that pattern, and we think that's a great lesson. Another thing we really love are all the pop culture references and information about various settings. It was so cool when our son heard a recording of Frank Sinatra and shouted, "It's the Rat Pack!" (See: "The Wonder Pets Save the Rat Pack," an adorable band of rats who need help working together.) He saw the fake Eiffel Tower at Disney World and shouted, "It's the Eiffel Tower!" (See: "The Wonder Pets Save the French Poodle.") He knows about volcanoes, New York City, magicians, nursing homes, and circuses, all from the Wonder Pets -- and he hasn't watched in a long time, so this stuff "stuck" really well. And finally, of course, it's extremely gentle, completely nonviolent, reinforces parent/kid relationships while still showing animals being independent, and full of great role models. The wise words of Linny the guinea pig helped us many times while our son was adjusting to his new baby sibling. :o)
Our son is now four and watching other stuff (in large part because he's seen all the "Wonder Pets" episodes), but I'd say "Wonder Pets" is still the highest-quality program for little kids that we've seen.