Nothing special really, it would just be guaranteed to hit. Accuracy in Pokemon and rpgs in general work like this: There is a value that is formulated which we will call "A" then the game will generate a random number from 1 to 100 (in gen I-II its 255) which we will call R. According to Bulbapedia, if R is less than or more than A, then it hits.
So R = 20 and A = 80? It hits. R = 75 and A = 80? It hits. R = 81 and A = 80? Doesn't hit.
In your example, A would be 108. Since R can only range from 1-100, it is guaranteed to hit every time.
Also there's some cool info about how A is calculated in the games in this source, in case you're interested.