CREATE TABLE t1 (a int);
 CREATE TABLE t2 LIKE t1;
ALTER TABLE t1 add key(a);
SHOW CREATE TABLE t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `a` int(11) default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
drop table t1, t2;
CREATE TABLE t1 (a int);
 CREATE TABLE t2 LIKE t1;
CREATE TABLE t2 (b int);
let's take a look at result of create .. like : 
-----------
ERROR HY000: Can't create/write to file './test/t2.frm' (Errcode: 17)
-----------

SHOW CREATE TABLE t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `b` int(11) default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
drop table t1, t2;