Apparently if it starts with a hex character it behaves differently.
```
> new Buffer('foo', 'hex');
TypeError: Invalid hex string
    at Buffer.write (buffer.js:348:25)
    at new Buffer (buffer.js:215:28)
    at repl:1:5
    at REPLServer.self.eval (repl.js:110:21)
    at repl.js:249:20
    at REPLServer.self.eval (repl.js:122:7)
    at Interface.<anonymous> (repl.js:239:12)
    at Interface.EventEmitter.emit (events.js:95:17)
    at Interface._onLine (readline.js:202:10)
    at Interface._line (readline.js:531:8)
```