Beast Boy kept his grin, before giving a slight shrug. "Squirrels are small... anything bigger than you, it takes a lot of energy and concentration." The shapeshifter thought a moment on most of his transformations; the t-rex and pterodactyl were often used, but did take a lot of concentration, as well as his energy if he did it too often in one setting.

Technically though, Gar could only do this because of what Kronk would consider spells and potions... he didn't look like someone of a present time-standing, and Beast Boy didn't even really have to ask to know. When you hang out with a half-robot guy and a boy wonder with gadgets of tomorrow, you tend to figure that kind of thing out.