Welding a zombie, please help?

I am making a zombie game, I have a zombie which I want to add parts to (like a hat, for example). I used this script to do so:

local function weldBetween(a, b)
    local weld = Instance.new("ManualWeld")
    weld.Part0 = a
    weld.Part1 = b
    weld.C0 = CFrame.new()
    weld.C1 = b.CFrame:inverse() * a.CFrame
    weld.Parent = a
    return weld;
end

script.Parent:WaitForChild("Torso")

for i,v in pairs(script.Parent:GetChildren()) do
    for a,b in pairs(script.Parent:GetChildren()) do
        if v:IsA("Part") and b:IsA("Part")then
            weldBetween(v,b)
        end 
    end
end

Anyway, my issue is that the zombie loses his walking animation because his leg is welded on, what can I do to stop this? If I don't weld him together wont he just fall apart?

Question number two is, how would I go about giving the zombie an animation for hitting someone, can I use cframe to do so, should I make an animation and upload it? Thanks.