Wall for Your Excellency (page 1)

One of Heatran's pokedex entries says it is made of steel, but is melted in places. That would make the horns metal, and not a defined shape. They can melt and move around before cooling. They would look different on other Heatran if there was more than one in the canon. At least I see it that way.
Heatran does not move by hopping, but it does to turn. You might say they all do, but in raids in pokemon GO it does a little (but still noticeable) hop to the side, while charizard blastoise just turns.
Also, how does heatran resemble Vah Rudania? I'm genuinely confused. I mean yeah, they're both lizard-like. So is the Bulbasaur line.

It’s still a frog in my eyes

‘I have proof Heatran is a frog. It has no visible neck or tail (The pointy part is not a tail, as it would be much narrower) It has the large eyes, squat pose, and broad mouth of a frog or toad, it crawls onto walls and ceilings, something other frogs can do (Greninja) and last, it hops.’
- SlitherWing

Freaking dang it I knew someone would do that!

Seriously read the comments if it still dosent look like a frog

https://www.reddit.com/r/pokemon/comments/b33ym1/im_not_doing_the_title_thing_heatran_without_armor/
you wont see it the same again... ever

Or If that dosent work search, ‘is heatran a frog? Or ‘naked sinnoh legends’ one of those will work

I can prove that heatran is a frog! Search ‘naked heatran’ don’t worry it’s just heatran without its armour on, not anything… weird. Anyway it just looks like a silly magma frog.

Also merry Christmas

I am promoting you to commander
Your welcome (: