Normally OP_INVALIDOPCODE would cause script evaluation to return false, but what if it is inside the scope of a pair of OP_IF .... OP_ENDIF?
Take a look at this tx:
77822fd6663c665104119cb7635352756dfc50da76a92d417ec1a12c518fad69
scriptPubKey is
OP_IF OP_INVALIDOPCODE 4effffffff 46726f6d.... OP_ENDIF
It seems that a scriptSig of the following will be accepted to memory pool, but will it still fail to verify?
OP_1 OP_0