Pokemon that change form dramatically when evolving

[Nikorasu]

to

WTF HAPPENED

 

[PartiallyInsaneWhimsicott]

^ This. Puberty hits fast, I guess.

How about...

Geodude-->Golem

How does that little pebble of awesome evolve into that...weirdo turtle thing?

 

[Kotowari]

Venipede - Whirlipede - Scolipede (once again a "butterfly" species)
Sewaddle - Swadloon - Leavanny
Yamask - Cofragrigus
Tynamo -Eelektrik (/Eelektross)
Shellmet and Karablast evolines

 

[King Of The Blues]

More from me, lol.

Surskit - Masquerain.

Oddish - Gloom.

Lileep - Cradily.

Drowzee - Hypno.

 

[Chiar]

Pupitar - Tyranitar
Chingling - Chimecho
Cherubi - Cherrim
The biggest change in evolution stages is Remoraid -> Octillery for me.[/font

 

[Mahou Tsukai]

Thats quite a list!
And from looks alone, one can't tell that Dragonite evolved from Dragonair.

 

[miju-kun]

Ralts--Kirlia--Gardevoir
Ralts--Kirlia--Gallade
Chingling--Chimecho
Vulpix--Ninetales
Lilipup--Herdier--Stoutland
Smoochum--Jynx
Shelgon--Salamence
Trapinch--Vibrava
Dewott--Samurott
Bonsly--Sudowoodo
Drowzee--Hypno
Zwelious--Hydreigon
Gothorita--Gothitelle
Duosion--Reuniclus