When I was a kid and I watched The Powerpuff Girls, I used to mishear the credits theme's line "Bubbles, she is the joy and the laughter" as "Bubbles, she likes to play with the water". Not too bad? Well, I misheard "Buttercup, and she's the toughest fighter" as "Buttercup, and she's a topless spider".
And this isn't something I misheard, but my friend said she misheard "Blossom, commander and the leader" as "Blossom, she really is the leader".
A childhood belief about misheard lyrics

others believed things like this
- If you held a buttercup under your chin and got a yellow reflection then you liked butter!— Tilly
- A common misheard lyric in BMTH’s ‘Shadow Moses’ is “THIS IS SANDPIT TURTLE!”— Oli
- When I first heard Stawberry Fields Forever, I misheard the lyrics as Strawberry Fields For Trevor.— Matt
- In 'Call Me Maybe', I misheard 'Ripped jeans skin' as 'Rich cheese skin'. — Carly Rae Cheddar
- I used to think when you farted, bubbles came out.— Nick
- I thought a Prime Minister was some kind of religious leader, due to the "Minister" part— Darth Carrietta