Another member of the 'Ponibots'(?), Pinkie Pie herself.

Possible Scout for the group, probably something akin to Bumblebee? The only thing that comes to mind for her alt-form is an ice cream truck. Though unlike Fluttershy, her hair doesn't mysteriously disappear… but instead helps form the ice cream cone on top of said truck?

something random. Tempted to try and 'round out' the mane six… and maybe some villains