Could you possibly PM me about egg moves if it's diffcult to explain in the thread? You see, I've never done breeding in the original games so I've no idea how it works although I've seen some information about in it Bulbapedia. For instance Tentacool:I don't question having unique attacks. I agree, it's a nice mix-up. However, it still should be one that can be legally learned. Why not look at the Egg moves and assign one of them (or two if they come from the same father) to the opposing Pokémon? Poison Jab/Water Pulse/Muddy Water/Tickle, for example, is a legitimate moveset because Omastar could legitimately be the father, and it would even support having that in the party if you wanted to include it; meanwhile, Poison Jab/Water Pulse/Muddy Water/Confuse Ray is NOT legitimate as you need two fathers to pull it off (I don't think it gets passed from a mother that knows it as an Egg move).
You could also use a Move Tutor move, like Sleep Talk, so if you put it to sleep it can still attack you or Tickle you into weakness. Any of these can be legit., even a full four moves from that list (though unnatural).
I for one do not personally believe a Pokémon can suddenly learn Thunder because it lives in an electrical environment. If a Pokémon cannot learn a move, it cannot learn a move. If, however, surprise moves are thrown in like breeding moves and move tutor moves (in the former case having the father in the party is an excellent support for it as well), then I'm all for it.
Cyclone
https://bulbapedia.bulbagarden.net/wiki/Tentacool_(Pokémon)
You'll get a Tentacool with Aurora Beam when breeding female Tentacool/Tentacruel with Shellder/Cloyster which knows Aurora Beam, right? Wouldn't you be able to do the same with any other male pokemon that knows Aurora Beam too or is that just one possible example in there?
What I'm trying to get with this is that, could you possibly breed female Tentacool with male Raichu which knows Thunder to get a Tentacool which knows Thunder if I hacked Thunder as Tentacool's egg move learning data so that it could learn it along with the other possible moves in 2nd gen?