It's a little hard to tell unless their side by side, by Liar has a slightly brighter color palette than Tyke. This is also the only expression he makes, so he has this sinister look on at all times.

Liar can also be seen spying on Tyke at times, but he also isn't really acknowledged at all. Maybe Liar can only be seen if he wants to be. He is also completely silent.

original - https://www.furaffinity.net/view/59489722/