(Headcannon)
It takes a lot of concentration for Janus not to lie so when he gets really upset, emotional, or distracted he gets a very severe "accent" where he lies wayyyy to much.

(Prompt)
Janus >Deciet< gets very emotional/upset at Patton and starts angrily lying at the sides.

>example:  Janus says;
"Me, fun mom-like front that effects none my happiness, are not jokingly rubbing on your muscles left tomorrow!"

When he actually means "You, annoying dad-like side that causes all my frustrations, are seriously grating on my nerves right now!"<