Old (possibly '80s?) cartoon/anime with male kids/youngsters. I think I remember one main boy character that loves the princess, one with glasses, and a chubby one. They find a landed spaceship with flashing lights and go on a space journey on a space boat with a princess for some quest, maybe to save her kingdom. It aired in Greece and was dubbed in Greek. It was possibly an anime or cartoon. Sorry, I don't remember much.
This is Byeolnara samchongsa (1979)
Three young children are fascinated by space. One night they saw a flying object crashing into the forest. Ruru, the king of the children of the kingdom of the space is on board. Ruru invites the three musketeers in his realm of space. During this journey, a terrible battle began in space to destroy the enemy in the middle of a meteor shower.
I was searching it to all these years!