While shattering ultra-conservative Catholic stand on many modern-day lifestyles which draw people to the church, Pope Francis also showed his now famous humorous side.

On Monday, the pontiff stressed the importance of the Catholic sacrament of baptism, saying it should not be refused, especially to infants or children whose parents may be considered violators of the church's rules such as those who are living in and not married.

A few weeks ago, he demonstrated he showed what he preached by baptising the child of an unwed mother and telling the lactating mothers inside the famous Sistine Chapel not to hesitate to breastfeed their babies in the church - with the ceiling paintings of Renaisssance artist Michaelangelo as witnesses - if the little ones get hungry during the rites.

Jokingly, he even said if aliens such as "green men with long nose and big ears" arrive and seek baptism, the church should also extend to them the sacrament that represents the entry of a person into the Christian world and removes the original sin caused by Adam and Eve's disobedience to God.

"If tomorrow, for example, an expedition of Martians arrives and some of them come to us ... and if one of them says: 'Me, I want to be baptized!' what would happen?" Pope Francis asked.

He stressed that it is not up to Earthlings to decide who should receive the Holy Spirit, whom Catholics receive in their life upon baptism.

Pope Francis made the remarks as part of a church discussion on the early Church's baptism of Gentiles or non-Jews who eventually converted from paganism to Christianity.