You could edit the grub executable and replace the title with a string of the same length. A feature of ELF format is that there's no checksum.
On my Debian 7, that's (found using
grep -l 'GNU GRUB') in
od shows uses a nul-terminated string:
726f 616d 206c 6e65 6976 6f72 6d6e 6e65
0153140 t \0 > \0 g r u b > \0 G N U G R
0074 003e 7267 6275 003e 4e47 2055 5247
0153160 U B v e r s i o n % s \0 1
file command tells you about the format, e.g.,
$ file /boot/grub/normal.mod
/boot/grub/normal.mod: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped
Of course, you should use a suitable tool for this, such as a hex-editor.