Here's a dolphin specially ordered by Mikikko! Be sure to stop by her page and say a cheerful hello!

This product is for FEMALE only and has a couple of quirks. You can't "put back" this pet in the IMVU inventory. Instead you must click on the "Avatar" entry in inventory to open it. There look for the "....apply" next to your desired gender of avatar. Click the "apply" button. Your pet should now be back in inventory.

The trigger command is "ridem" (no quotes). Your avatar should get on his back and ride him around in a circle. You may want to pull the camera back a little, so you can see the whole ride. When your not riding him, he'll float next to you treading air.