This website contains age-restricted materials including nudity and explicit depictions of sexual activity.
By entering, you affirm that you are at least 18 years of age or the age of majority in the jurisdiction you are accessing the website from and you consent to viewing sexually explicit content.
But the whole point of the gag is to subvert our expectation of what happens when a princess kisses a frog. If the frog doesn’t appear until the end, then where are we going to get our expectation from?
You still see the frog on the wall in the first and third panels, you just might not notice it’s colorful so the comic has a chance to do that subversion and surprise at the end.
With the way it’s structured now you aren’t surprised by the ending because it’s very clearly a poisonous looking frog.