Characters from top left to bottom right:

Girlfriend (Friday Night Funkin')

Boyfriend (Friday Night Funkin')

Hank J Wimbleton (Madness Combat)

Tricky the Clown (Madness Combat)

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Tom Fulp

Strawberry Clock (Clock Crew)

Pico (Pico's School)

Nene (Pico's School)

Darnell (Pico's School)

Jerry Jackson (Jerry Jackson)

Salad Fingers (Salad Fingers)

Blockhead (Blockhead)

Henry Stickmin (Henry Stickmin)

Alien Hominid (Alien Hominid)

Phil Eggtree (Riddle School)

Edd Gould (Eddsworld)

Sergeant John Captain (Tankmen)

Steve (Tankmen)

Fancy Pants Man (Fancy Pants Adventures)