That silly eye-candy boot is Plymouth, I hate that thing. In fact, I am going to uninstall it right now. Hopefully it won't render my OS unusable too.
Anyway, in the good ole days when I used Slackware, I used to be able to halt the boot while the Grub menu was showing, then press 'e' to edit the corresponding boot entry, then add '3' to the end of the kernel line, then press 'b' to boot. That would force a pure command line boot, without the desktop environment. Adding '1' instead of '3' to that line would force single-user mode. Either option should be enough to let you boot the system and do some repair work.
But that was Slackware. Ubuntu adds some interference here and there, like removing Ctrl+Alt+Backspace, so I am not sure that backdoor will be available in Ubuntu. As a last resort, you may want to try a rescue CD like System Rescue CD
. There is a USB stick version, too.