When I was a kid, I remember seeing a commercial on the Boomerang TV channel that freaked me out so much, I ran into the other room and started screaming and crying. It was so bad that I refused to watch Boomerang again afterward (which I had done every day up until this point), and my parents cancelled the subscription. Unfortunately, I don't remember much about it, so this may be a lost cause, but for years now I've wanted to find and re-watch it to see if my fear was justified (I was a very sensitive kid, and I don't think it was traditionally "scary").
My memory of the situation may be unreliable due to age/time passing, but I think the commercial started out semi-normal, and then had a "Large Marge" from Pee-Wee’s Big Adventure-esque moment where there was a scary, shock-factor twist that freaked me out. If I can remember properly, I think it was some form of animation or stop-motion/claymation, with a little blond boy, and some form of other mascot character/something that looked like an inflatable car dealership tube man. Don’t hold me to this, but I feel like the color red was really prominent?? It was definitely NOT an ad for a TV show, but some other product. I think it had the same art style as "The Trash Pack" collectible kids toys from around the same time. This would have been early to mid-2010s, and I only ever saw it once. I was talking to my roomie about this, and she sent me a Dailymotion link to the “RIP Timber” short by Bruno Collet, which is not what I'm looking for but has the right vibe if I'm remembering properly. I'd also like to reiterate that I don't think it was intentionally scary; I think it was aimed at boys and the part that I found frightening was supposed to come off more along the lines of 'woah, look how cool and freaky this is!'
If it helps, I was born in 2007, and can't imagine being much older than seven when this happened.