For more than 20 years, Green Day have been churning out three chord pop-punk gems that make you feel like you're 15 years old again (and if you're 15 and reading this now, you'll understand one day). They do it really well. Sometimes too well. But there's a good reason why some of those catchy riffs cut right into your brain -- you may have heard them before.

We're not accusing Green Day of intentionally stealing musical ideas, as all the comparison examples below could be purely coincidental. In fact, further down this list, there are cases where the scenario is reversed.

Let's have a listen below!

Pokemon/Mott the Hoople/Electric Light Orchestra vs. Green Day

You'll never be able to listen to any of these songs again without thinking about Pokémon.

Listen to Pokémon Diamond and Pearl Game Music (2006)

Listen to Mott the Hoople, 'All the Young Dudes' (1972)

Listen to Electric Light Orchestra, 'Telephone Line' (1976)

Listen to Green Day, '21 Guns' (2009)

Petula Clark vs. Green Day

Billie Joe Armstrong even starts the line with "downtown." Coincidence?

Listen to Petula Clark, 'Downtown' (1964)

Listen to Green Day, 'Waiting' (2000)

The Kinks vs. Green Day

You'll be so sure that you're listening to the Kinks. Or wait! Are you listening to Green Day?

Listen to the Kinks, 'Picture Book' (1968)

Listen to Green Day, 'Warning' (2000)

Scott McKenzie/Neil Young vs. Green Day

Turn your black light on and play them all at the same time with headphones.

Listen to Scott McKenzie, 'San Francisco' (1967)

Listen to Neil Young, 'Heart of Gold' (1976)

Listen to Green Day, '21 Guns' (2009)

'Full House' vs. Green Day

The guitar riff in this comparison sounds eerily similar to the 'Full House' theme song.

Listen to 'Full House' Theme, 'Everywhere You Look' (1987)

Listen to Green Day, '21 Guns' (2009)

Bryan Adams vs. Green Day

"City of the dead / At the end of another lost highway / Those were the best days of my life."

Listen to Bryan Adams, 'Summer of 69' (1984)

Listen to Green Day, 'Jesus of Suburbia' (2004)

Korean Song vs. Green Day

We have no idea what this is, but comments on YouTube suggest that this Korean song came out first.

Listen to This Korean Song

Listen to Green Day, 'American Idiot' (2004)

Green Day vs. Steve Earle

Maybe Steve Earle had never heard a Green Day song before. Or had he?

Listen to Green Day, 'Basket Case' (1994)

Listen to Steve Earle, 'Here I Am' (1997)

Green Day vs. Blink 182

Listen to the guitar riff.

Listen to Green Day, 'Basket Case' (1994)

Listen to Blink 182, 'What's My Age Again' (1999)

Green Day vs. Ovaltine Commercial

We have no explanation for this other than it sounds exactly like Green Day's 'Basket Case.'

Listen to Green Day, 'Basket Case' (1994)

Listen to German Ovaltine Commercial (2005)