Changing the font/size on the username inside the chat box

This publication contains the options to customize the text.

local chatService = require(game.ServerScriptService:WaitForChild("ChatServiceRunner"):WaitForChild("ChatService"))
chatService.SpeakerAdded:Connect(function(playerName)
	local speaker = chatService:GetSpeaker(playerName)
	speaker:SetExtraData("Font", Enum.Font.FredokaOne)
	speaker:SetExtraData("TextSize", 40)
end)

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