Define The Smartest Kid On The Short Bus Meaning

The Smartest Kid On The Short Bus
A metaphor for being the best at something that's unimportant or unimpressive. For example: The fastest pitcher who lives at a nursing home is like being the smartest kid on the short bus.

It comes from the special bus designated for retarded people commonly being shorter than the others.

Zack: I'm the best guitar player in town
Me: Whatever, that's like being the smartest kid on the short bus
By Nert