The Missing PRESS START BUTTON text glitch is a glitch that occurs in the Sega Mega Drive/Genesis game Sonic the Hedgehog. The "PRESS START BUTTON" text that appears on the title screen in early prototype screenshots never appears in the final game, unless it is hacked.
The glitch occurs because RAM isn't properly cleared, the byte that allows the text to be shown is shared with the two previous screens before the Title Screen and therefore the value is stuck in a no call state, rendering the text to never show up. A more thorough technical explanation of the glitch and fix can be found in this topic from Sonic Retro.(see here)