Thomas Built Buses OMV-13

The Thomas OMV-13 is a successor to the FS-65. The OMV-13 was the replacement for the saf-t-liner model  based on the F565. It uses the International 3300 chassis.

Concept Art
The Thomas Built Buses OMV concept is somewhat based on a 1970s Ward International bus (and a 2003 Bluebird A3RE) with fender skirts on the rear wheel, the front windshield being 2 different windows, a grille spine down the center of the grille, the exhaust (which is small) coming out of the roof, and the supercharger's big intake pipe underneath the rear bumper (for the CNG variant only).

Livery
In the concept art and the original LAUSD variant, the model was painted fully Walkerville yellow. In one of the final models it is painted in the common North American School Bus yellow with black stripes.

It isn't really clear how The Magic School Bus works, but there are some hints in the TV series. We can see the how the fuel gets to the engine in "[Up| Revving Up]". First of all, its magic seems to flow from several unusually named devices, like the Shrinker Scope or the Mesmerglober. The Shrinker Scope serves mostly as an easy way to shrink and resize the bus at the will of Ms. Frizzle. It seems to have at least two varieties of the Shrinkerscope, namely, the main one (as an internal part) and the PortaShrinker. At least the latter can't work when damp or wet, and if someone attempts to activate it in such conditions, the Dew Dinger sounds.

The Mesmerglober, on the other hand, is primarily concerned with changing the shape of The Magic School Bus. It changes it into whatever the class needs, be it a bus-marine, a spaceship, or a bus-igator.

In the episode Making Magic, it pretty much reveals where the Bus's magic comes from: a Magic Battery (Mag-Batt for short) and it runs on solar power with actual energy from the center in the sun, as well as true courage and perseverance as revealed by Fiona Frizzle herself.

Trivia

 * The bus was able to float around in lava this may lead to that the bus may be physically indestructable
 * The Magic School Bus seems to have a deep caring for the students in [Frizzle| Ms. Frizzle]'s class. This is displayed in [Ants in Its Pants| Gets Ants in Its Pants] when it is pouring with rain and it graciously offers [| Keesha] the chance to get dry by getting in. She declines, arguing she "deserves" to get wet and the viewer can see The Magic School Bus pity her as she sits on a wet log.
 * The Magic School Bus reveals to be sentient, mainly due to having eyes and a mouth. This is further in shown in [Flight| Taking Flight] when it gets angry at [| Liz] for constantly making it crash when [| Tim] and [Terese| Phoebe] were trying to save the rest of the class, in the opening when it looked a bit scared upon seeing an octopus in the neighborhood, and in [Lost in Space| Gets Lost in Space] when it felt exhausted upon Janet overloading it with "proof" she went to all the planets of the Solar System. It is shown The Magic School Bus is incapable of talking, but it is capable of panting and coughing and the famous honking is used for talking as revealed in [Magic School Bus Rides Again| Rides Again] . It's also unknown what gender The Magic School Bus is.
 * The Magic School Bus has few modifications throughout the series, which include:
 * Original Series:
 * It had fender skirts covering its rear wheels.
 * Rides Again:
 * Its fender skirts are removed from the rear wheels, thus revealing its rear wheels.
 * Back Antennae and roof hatch are added.
 * On the back, it has two doors instead of one.
 * Its bottom lip is a darker shade of silver than its top lip.
 * Its headlight eyes turn light aqua.
 * It now has one extra window on its sides.