Sometimes when I’m playing something like the Piper there’ll be a something that looks like a green sprout and when i jump on it it disappears. Does it actually do anything? Because it doesn’t seem like it
You can unlock new characters.
Some characters can only be unlocked by collecting certain items.
- Coconut Water – While using the Tourist (either by purchasing or winning him), collect at least 5 coconut cocktails.
- Bones – While playing as the Palaeontologist, pick up each of the dinosaur bone pieces dotting the map. Complete a full set, and you’ll be awarded with this skeletal ally upon your death.
- Hipster Whale – No better place to start than the company mascot. Hipster Whale will appear swimming amongst the logs during gameplay. All it takes is to hop on his back, and you’ll unlock him as a playable character.
- The Totem – While playing as any of the characters from Monument Valley, spot the Totem drifting down the river. Like the Hipster Whale, board it to unlock it.
- Nessie – Sensing a theme here? Use any of the UK or Ireland characters, and be on the lookout for Nessie in a body of water. Hop aboard, and Nessie will be yours.
- Michael Boom – This character isn’t hard to acquire, but it will cost you your life. Just keep your eyes peeled for a green truck carrying a rocket. Collide with it, and you’ll appropriately go up in flames. When the dust settles, you’ll have a new addition to the roster.
- Yeti – While playing as any of the Christmas ’15 characters, find the Yeti on the field, flinging snowballs. Put yourself in the line of fire, and you will lose your life, but gain this abominable friend.
- Chinese Monster – While playing as the New Year’s Doll, find the Chinese Monster on the map. Catch it, and you will unlock it henceforth. Super lucky!
- Leprechaun – Faith and Begorrah! Play as any of the UK or Ireland characters, and scoop up every clover you see. Rarely, one will be a lucky four-leaf one, which will net you the Leprechaun.
- Rugby Player – To unlock the Rugby Player, you’ll need to first use the Squirrel. Make sense? Not really, but you’ll have to collect four nuts in trees on a run, after which a rugby ball will appear stuck in a tree (it looks like a white nut). Grab that, and you’ll be able to join the scrum.
- Gifty – While playing as the Festive Chicken, keep progressing until you reach a snowy plain. Collide with the Christmas Tree, and a mess of presents will spill out. Afterwards, you will receive Gifty.
- The Princess of All Cosmos – A lengthier title in Crossy Road, there may not be. While playing as the Prince of All Cosmos, amass around 12 items in your Katamari ball to unlock her.
Ace – While playing as Rocky, gobble up at least 50 burgers across multiple runs, and achieve a high score. Doing so will net the former Jughead.
Pinky – selecting the Pac-Chicken, obtain the famous cherries hidden on the map.
Clyde – A little more tricky than his brethren; Clyde requires you to play as Pac-Man, and eat 7 or more ghosts on the one power pellet. It’s much easier said than done.
Information copied from https://twinfinite.net/2018/07/crossy-road-all-hidden-characters-how-get/