It happens because the double exclamation mark is expanded by the shell as "the last executed command" (see the BASH history explanation in your guide). When you use !! the shell first prints out the command to execute, then the output of the command itself. For example:
In your case you get the reprint of the command line with !! expanded as the last executed command (in blue below), then its output (the output of the entire echo command - in red below).
$ set I am the king
$ echo $1 $2 $3 $4
I am the king
$ echo $1 $2 $3 $4 who do u think u r!!
echo $1 $2 $3 $4 who do u think u recho $1 $2 $3 $4
I am the king who do u think u recho I am the king
To prevent the shell to interpret !! as a history command, you have to use single quotes or escape the exclamation marks using a backslash. That is both the following commands should work as you expected:
$ echo $1 $2 $3 $4 who do u think u r'!!'
$ echo $1 $2 $3 $4 who do u think u r\!\!