SCUMM: MANIAC (Original bug): walking on background in entrance hall
In all the enhanced ports of Maniac Mansion (Amiga, Atari, PC), there is an original interpreter bug in the entrance hall, which is very easy to replicate. Walk two or three steps up the stairs, then click to the right of the vase to the right, and the character walk through part of the stair railing and the vase. How that looks, see screenshots made under ScummVM.
Clearly the area where a character can not walk was not set correctly (it was set correctly on the C64).