Recently when i was searching for hidden screens in Puggsy i saw a screen that said "O.K. thats all the levels of puggsy your allowed to play, no go and play a cartidge version of the game instead of this silly copy. until then......bye. travellers tales 93"
So this is probably a anti-piracy screen, but how did the game know when it was a pirated copy of itself?
Excerpt from The Cutting Room Floor
"Although the official retail Puggsy cart does not contain SRAM, the game attempts to write to it anyway, in order to detect third-party copying devices (which always contain SRAM). If the write is successful, the game will appear to function normally. However, the player won't jump as high as normal. In addition to this, after clearing a few levels, the game will stop and present the player with a personal "gotcha" message from the Traveller's Tales devs themselves. Rather infamously, many emulators which blindly create SRAM regions for each game will also trip the check.
The game also tries to prevent these tests from being easily detected and removed — there are six write checks split into three sets, with one of them stored at the end of a subroutine called four times throughout the game, another checked once immediately before one instance of the subroutine call is executed, and the third in a vertical interrupt routine. The SRAM address the game checks also cannot be detected easily, as the game loads an address some random distance away from the actual address and adds the distance immediately afterward through lea instructions. All checks have different base values and distances."