Search giant Google is celebrating its own 20th birthday today with a trademark Doodle.

Replacing its logo with an occasional animation paying tribute to eminent figures from the worlds of science, the arts and history on their anniversaries is just one of the ways in which the site’s programmers can express themselves.

Their quirky sense of humour is actually embedded within the software's DNA.

The best Google Doodles Show all 50 1 /50 The best Google Doodles The best Google Doodles Mister Rogers Google Doodle celebrating children's TV presenter Mister Rogers Google The best Google Doodles Lucy Wills Google Doodle celebrating haematologist Lucy Wills Google The best Google Doodles Falafel Google Doodle celebrating falafel Google The best Google Doodles St George's Day Google Doodle celebrating St George's Day Google The best Google Doodles James Wong Howe Google Doodle celebrating Hollywood golden age cinematographer James Wong Howe Google The best Google Doodles Seiichi Miyake Google Doodle celebrating Seiichi Miyake, developer of tactile paving Google The best Google Doodles Walter Cronkite Google celebrates US broadcast journalist Walter Cronkite's 100th birthday The best Google Doodles Lantern Festival 2016 Google celebrates the last day of the Chinese New Year celebrations with a doodle of the Lantern Festival Google The best Google Doodles Google Doodle celebrating Sergei Diaghilev Google Doodle celebrating art critic Sergei Diaghilev Google The best Google Doodles George Boole Google marks mathematician George Boole's 200th birthday The best Google Doodles Sergei Eisenstein Google Doodle celebrating soviet film director Sergei Eisenstein Google The best Google Doodles 41st anniversary of the discovery of 'Lucy' Google marks the 41st anniversary of the discovery of 'Lucy', the name given to a collection of fossilised bones that once made up the skeleton of a hominid from the Australopithecus afarensis species, who lived in Ethiopia 3.2 million years ago The best Google Doodles Elizabeth Garrett Anderson Google celebrates physician and suffragist Elizabeth Garrett Anderson 180th birthday The best Google Doodles Sir William Henry Perkin Google Doodle celebrating chemist Sir William Henry Perkin Google The best Google Doodles Nelly Sachs Google Doodle celebrating poet and playwright Nelly Sachs Google The best Google Doodles Thanksgiving 2018 Google Doodle celebrating Thanksgiving 2018 Google The best Google Doodles Nigerian Independence Day Google Doodle celebrating Nigerian Independence Day Google The best Google Doodles Mary Prince Google Doodle celebrating abolitionist Mary Prince Google The best Google Doodles Father's Day 2016 Google celebrates Father's Day The best Google Doodles Ebenezer Cobb Morley Google Doodle celebrating "father of football" Ebenezer Cobb Morley Google The best Google Doodles Octavia E Butler Google Doodle celebrating science fiction author Octavia E Butler Google The best Google Doodles Tamara de Lempicka Google Doodle celebrating painter Tamara de Lempicka Google The best Google Doodles Johann Carl Friedrich Gauss Google Doodle celebrating mathematician and physicist Johann Carl Friedrich Gauss Google The best Google Doodles Fanny Blankers-Koen Google Doodle celebrating Dutch Olympic gold medalist Fanny Blankers-Koen Google The best Google Doodles John Harrison Google Doodle celebrating clockmaker John Harrison Google The best Google Doodles Guillermo Haro Google Doodle celebrating astronomer Guillermo Haro Google The best Google Doodles St. David's Day Google Doodle celebrating St. David's Day Google The best Google Doodles Carter G Woodson Google Doodle celebrating Carter G Woodson, a pioneering African-American historian Google The best Google Doodles St Andrew's Day Google Doodle celebrating St Andrew's Day Google The best Google Doodles Gertrude Jekyll Google Doodle celebrating horticulturist Gertrude Jekyll Google The best Google Doodles Children's Day 2017 Google Doodle celebrating Children's Day 2017 Google The best Google Doodles Studio for Electronic Music Google Doodle celebrating the Studio for Electronic Music Google The best Google Doodles Olaudah Equiano Google Doodle celebrating abolitionist Olaudah Equiano Google The best Google Doodles Fridtjof Nansen Google Doodle celebrating Norwegian explorer Fridtjof Nansen Google The best Google Doodles Ladislao José Biro Google celebrates Ladislao José Biro's 117th birthday The best Google Doodles Amalia Hernandez Google Doodle celebrating ballet choreographer Amalia Hernandez Google The best Google Doodles Dr Samuel Johnson Google Doodle celebrating lexicographer Dr Samuel Johnson Google The best Google Doodles British Sign Language Google Doodle celebrating British Sign Language Google The best Google Doodles Eduard Khil Google Doodle celebrating baritone singer Eduard Khil Google The best Google Doodles Fourth of July Google Doodle celebrating Fourth of July Google The best Google Doodles Victor Hugo Google Doodle celebrating author Victor Hugo Google The best Google Doodles Google Doodle celebrating Giro d'Italia's 100th Anniversary Google Doodle celebrating Giro d'Italia's 100th Anniversary Google The best Google Doodles Google Doodle celebrating St. Patrick's Day Google Doodle celebrating St. Patrick's Day Google The best Google Doodles Google Doodle celebrating St. David's Day Google Doodle celebrating St. David's Day Google The best Google Doodles Steve Biko Today's Google Doodle features anti-apartheid activist Steve Biko Google The best Google Doodles The history of tea in Britain Google celebrates the 385th anniversary of tea in the UK The best Google Doodles Nettie Stevens Google celebrates geneticist Nettie Stevens 155th birthday The best Google Doodles William Morris Google celebrates English polymath William Morris' 182 birthday with a doodle showcasing his most famous designs Google The best Google Doodles Professor Scoville Google marks Professor Scoville’s 151st birthday The best Google Doodles Sophie Taeuber-Arp Google marks artist Sophie Taeuber-Arp's 127th birthday

If you type the word ”askew” into its search box, for instance, the results will appear tilted at an extreme angle.

If you tell Google to “do a barrel roll”, the whole page will spin clockwise at 90 degrees before juddering to a stop.

If you search for “the answer to life the universe and everything”, you’ll be presented with Google’s calculator displaying the number 42, an in-joke alluding to Douglas Adams’ cult science fiction series The Hitchhiker’s Guide to the Galaxy (1978).

Google is full of these neat little Easter eggs.

An entry for “zerg rush” will see little red circles swarm your screen and devour the search results, another reference, this time to the video game StarCraft (1998).

Searching “define anagram” will see you offered the alternative, “Did you mean: nerd fame again”, while entering the phrase “once in a blue moon” will give you a calculation explaining precisely how to work out how often the phenomenon occurs: 1.16699016 × 10-8 hertz.

A nice one embedded in Google Maps for JRR Tolkien fans appears if you ask for directions from “The Shire” to “Mordor” and choose walking as your preferred method of transport. Google’s reply? “Use caution – One does not simply walk into Mordor”.

In addition to these in-built gags, fans have made their own to manipulate Google.

More fun with Google can be had by playing the game “Googlewhack”.

Credited to Gary Stock, the game involves hunting for Google searches of no more than two words that yield a single result.

British comedian Dave Gorman popularised the concept with his 2003 stand-up comedy show, Dave Gorman’s Googlewhack Adventure!, in which recounted the true story of his being unable to finish the novel he was writing after becoming obsessed with the game.

The comic travelled the world meeting the owners of the businesses who rendered a single, solitary entry on Google and wrote about his experiences in a best-selling book.