It is written in the history books
Books of fearful crooks
Crooks such as this little fish
Who makes a slippery dish
Let's all get in line
Cause it's mating time

No mana sustain
Somehow causes others pain
Big damage, big haste
I got it down, copy and paste
Give it up for slapping others with his ****
Welcome to the House of Menaces: Fizz

Domination tree is standard: assassin with dashes. No further explanation needed

Biscuit Delivery : At 2:00, 4:00 & 6:00 gain a biscuit. When consumed the biscuit instantly gives 50 mana, permanently increasing your mana by 50. In addition, over a period of 5 seconds restore 10% missing health and mana. Paired with Corruption Potion start, decent sustain in lane, should not really have a reason to back until the first core item.

Time Warp Tonic : Consuming a potion and/or biscuit immediately restore 50% of the health/mana said potion would restore. Furthermore, gain 5% bonus move speed while under the effect of the potion.

The go to mythic. Damaging an enemy champion deals 125 (+ 15% AP) bonus magic damage and grants you 25% bonus movement speed for 1.5 seconds. Additionally it's mythic passive grants 5 ability haste for each legendary item (surprise tool it will help us later).

Dealing ability damage to a champion with an ability that is 700 units away or slowing, immobilizing or polymorphing reveals them and increases your damage dealt to them by 10% for 6 seconds. This is the catalyst. This makes Fizz a menace as it gives ability haste. His ultimate slows the target, knocking them up after 2 seconds. The R increases damage with range. For instance, at max range level 11-15 with 175AP: (400+120%AP)+10% = 610+10% = 671AP damage with just two items

After damaging a champion with 3 separate basic attacks or abilities within 3 seconds, gain 20% bonus movement speed, decaying to 10% over 2 seconds, and 40 ability power until exiting champion combat. Good chunk of AP and ability haste. Basic Q+W+AA combo procs the passive allowing for more burst or disengage with E.

Increases your ability power by 35% and grants a big chunk of AP. With this generous magnifer you can easily two ability an enemy carry instantly or low enough you could AA or W them for the kill.

2 seconds of stasis. Great defensive tool to delay your death buying time for team backup because death is inevitable. Some AP and haste as well.

LEVEL 18:
Total ability haste w/boots: 110
Cooldown Reduced: (110/210)*100 = 52%
Q cooldown = 3 seconds
W cooldown = 2 seconds
E cooldown = 4 seconds
R cooldown = 33 seconds
Max range R damage ≈ 1240AP
E damage ≈ 630AP
W damage ≈ 390AP

Just like the poem at the start said: "big damage, big haste". This build truly lives up to it. Level 18 ≈1200AP every 4 seconds & ≈2400AP every 30 seconds and even prior to level 18 still huge amounts of damage in short spaces. Perfect assassin playstyle; Fizz truly deserves his place in the House of Menaces. See you on the rift. Thanks for reading.