Pokémon cards can be worth up to £1.2million, meaning fans of the Japanese gaming franchise should check their stash to see if they have any worth serious cash.
Pokémon is a series of computer games and collectible cards focused on a fantasy world where humans catch and train cartoon monsters for sport.
The card game was launched in 1996 and there have been 34.1billion individual cards sold worldwide.
Some of these cards are worth nothing - but many are worth serious amounts of money to the right buyer.
Now financial website money.co.uk has analysed all the Pokémon cards sold on eBay to see which ones could earn the most when sold.
The most valuable one on the market is on sale for $2.4million Australian dollars - around £1.2million, but plenty are changing hands for tens of thousands of pounds.
Have you sold a valuable Pokémon card? Message mirror.money.saving@mirror.co.uk
Money.co.uk finance expert Salman Haqqi said: "Pokémon cards have rapidly grown as a popular alternative investment. The nostalgia combined with the iconic characters have certainly recaptured the imagination of many people - so much so, they are willing to spend thousands, if not millions to ‘catch them all’."
Here are some of the most valuable Pokémon cards in the world:
1) Pikachu - £1.2million
The ‘Japanese Old Back Pokémon Trophy Card NO.2 Neo Spring Battle PSA 9 Pikachu’ is listed on eBay for an astonishing price.
The card was made back in 2001 and is in mint condition.
2) Kangaskhan - £350,000
Sellers are asking for serious sums for the 'PSA 10 Trophy Kangaskhan Parent & Child Tournament 1998' card.
3) Joint place between Blastoise and Venusaur - £185,868
EBay sellers are asking for almost £200,000 for two separate cards - a '1st Edition Japanese Base Set No Rarity Blastoise 1996 PSA 10 Mint' and the '1st Edition Japanese Base Set No Rarity Venusaur 1996 PSA 10 Mint'.
4) Rayquaza - £73,062
For the same price as a luxury car, Pokémon fans can snap up an 'EX Deoxys # 107 Gold Star Rayquaza Holo PSA 10 Card'.
5) Ivysaur - £54,797
The near-£55,000 price tag is for the rare 'PSA 10 ITALIAN Ivysaur #30 1st Edition GEM 10' card.
But although the Pikachu character features on the most valuable card, it is not the most valuable character overall.
The most expensive cards actually feature the Starly monster - a sort of bird Pokémon.
Cards featuring Starly are worth a median price of £399.51.
Those with the character of Bidoof on are trading for £285 on average.
Charizard cards go for £150, Lugia ones for £149.99 and Umbreons for £142.
How to know if you have a valuable Pokémon card
One big clue is printed on the bottom of each card that lets you know roughly how rare it is.
A circle means common, a diamond means uncommon, a star means rare and a white or gold star means ultra-rare.
Additionally, holographic and first edition cards are typically worth extra.
There are also limited-edition cards that collectors can only get by going to special events or through competitions.
Remember hidden costs – it’s not simply a buy and sell exchange with Pokémon cards.
Don’t forget about shipping fees, tax liabilities on sales and storage costs. Storage is key to keeping cards in ‘mint’ condition and securing them from any potential damage.
