I had tested myself, 
's E Toxic Shot does not proc 
's slow effect, but 
's W Seastone Trident can proc 's slow effect with both passive and active form, while both being on-hit DOT effect abilities.
Is this a bug or is it intended to be that way?
Quepha3 votesIt's intended. Fizz's W counts as an ability, Teemo's E counts only as an on-hit effect.
The Deckowner1 votesthat is extremely unfair and toxic, it's the definition of favoritism.
Quepha1 votes[{quoted}](name=The Deckowner,realm=NA,application-id=3ErqAdtq,discussion-id=QKPckbOI,comment-id=00010000,timestamp=2016-02-13T23:09:12.650+0000)
that is extremely unfair and toxic, it's the definition of favoritism.
If Fizz and Teemo were remotely similar champions, you would have a point.
Unfortunately, reality intrudes on your wild accusations.
MunchCrunchLunch2 votesbut it works on chogath E? like what is this bullshit? its an on hit sure. but its still AN ABILITY. every champion in this game. has 4 abilities. his E is one of them. its an ability that gives him. ON HIT damage. fizz W is an ability. that gives him on HIT damage. double standards. fizz ability is just on a cooldown and teemo's isn't. its stupidity.
its intended but its again. a nerf to teemo. as it should apply the slow. because his E is an ability that gives him on hit effects. like seriously? does every ability in the game mention that it applies on hit effects and abilities but they still do.
you can get frozen mallet. and do the same thing you'd do with rylais. but you won't get any ap from it. its just a stupid indirect nerf.
his E isn't his passive. its an ability slot. if you want to end the dispute. put his E as his passive. and rework his stealth into an actual ability or something]
but then again. his E doesn't proc liandrys either so its really pointless to buy it on him as it won't burn. this is one of the reasons teemo is unviable. if he was able to proc rylais+ liandries off his E. he can potentially. kite. and be useful without getting absolutely destroyed by any champion with half decent mobility.
The Deckowner1 votesRito just hate as a champion, everything in the meta is against him while his kit is one of the most enjoyable and balanced kit by far (compare to other top laners who clearly has some unfairness in their kit such as juggernuts 
and some who simply has cancerous kit like 
's %hp true dmg).
I hate how he is such a interesting champion with an ult that provides a feeling of strategic game but whenever i pick him i am considered trolling.
MunchCrunchLunch1 votesbecause every big headed high elo player thinks this game should be taken seriously and fun isn't part of it.
The Deckowner1 votesBut we play this game for fun.
Picking a which i love to play=Fun
Playing Easy free elo champ and easily win by just facerolling(you know who i am refering to)≠Fun
Sneakyy XD1 votesIt's definitely intended for Teemo. It's hard to say whether or not it's intended for Fizz. My guess is it was intended for the active portion of his W and not the passive but they missed it and never bothered changing it.
FIzz's Q is also weird.
The Deckowner1 votesfizz q also procs rylai, and by definition is applies ability dmg and onhit effect.