Treecko - Snivy
Treecko's tail is a leaf and so is Snivy's.
They're the fastest starters in their generations and the weakest ones offensively too.
That's not true! Sceptile got quite a special attack, combine that with the fact that all grass moves were special in gen III as well as the fact it had access to the most powerful grass move at the time, Leaf Blade, it was quite deadly.
Also I don't think the 2 of them look similar at all. Treecko has got much larger arms and legs compared to Snivy, while Snivy has got a longer body. The tails are also quite different, treecko's isn't as flat as Snivy's. the Shapes of their tales is also quite different.