Changing boards on trains and at stations is actually quite common these days and TOCs have done it dozens of times.
Back in February 2015 SWT renamed many stations for one day only for Valentines Day on all of their CIS boards:
Addlestone - Admirestone
Ascot - Love Ascotly
Ash Vale - Ash Valentine
Barnes - Legally Barnes
Basingstoke - Beautiful Basingstoke
Beaulieu Road - Beaulieu & The Beast
Bedhampton - Breakfast In Bedhampton
Botley - The Botley Guard
Bracknell - Lady Bracknell
Chessington North - Kissington North
Chessington South - Kissington South
Clapham Junction - Cupid Junction
Dean - Torvil & Dean
Dorking - Darling Dorking
Fareham - My Fareham Lady
Farnborough - Four Weddings & Farnborough
Eastleigh - Truly Madly Eastleigh
Fleet - Fleeting Romance
Fulwell - Flirtwell
Godalming - Lovealming
Guildford - Gorgeous Guildford
Hamble - Too Hot To Hamble
Hampton Court - Hampton Courting
Hersham - His & Hersham
Hilsea - Notting Hilsea
Hinton Admiral - Hinton Admirer
Hook - Hook Line & Sinker
Hounslow - Hounslove
Isleworth - The Apple Of My Isleworth
Kew Bridge - Cute Bridge
Liphook - Lips Hooked
Liss - Kiss
London Road Guildford - Lovers Road Guildford
London Waterloo - London Waterlove
Motspur Park - Mots Purr Park
North Sheen - North By North Sheen
Overton - Loverton
Petersfield - Passionfield
Portchester - Pride & Portchester
Reading - The Reading Singer
Redbridge - Roses Are Redbridge
Richmond - Rich In Love Mond
Romsey - Romeo & Juliet
Salisbury - When Harry Met Salisbury
Sholing - Sleepless In Sholing
Strawberry Hill - Strawberries & Champagne Hill
Sway - Eat Sway Love
Surbiton - Sweet Surbiton
Teddington - Lost In Teddington
Thames Ditton - Thames Smitten
Twickenham - Breakfast At Twickenham
West Byfleet - West Byfleet Story
Woking - Wonderful Woking
Wokingham - Wokingham Heights
Woolston - Pretty Woolston
Worplesdon - Phwoarplesdon
Back in December 2016 SWT renamed many stations for one week leading up to Christmas on all of their CIS boards:
Alton - Angelic Alton
Basingstoke - Basingstocking
Bracknell - Bracknoel
Bournemouth - Baublemouth
Box Hill & Westhumble - Boxing Day Hill & Westhumble
Berrylands - Cranberrylands
Bitterne - Blitzerne
Christchurch - Christmaschurch
Chertsey - Chertsleigh
Chessington North - Chessington North Pole
Clapham Junction - Clapham Jingle Bells
Datchet - Bob Datchet
Dorchester South - Dorchestnut South
Dorchester West - Dorchestnut West
Effingham Junction - Elfingham Junction
Egham - Eggnogham
Eastleigh - Eastsleigh
Ewell East - Yule East
Ewell West - Yule West
Hamble - Glazed Hamble
Hedge End - Holly Hedge End
Hounslow - Hounsnow
Haslemere - Haslemyrrh
Horsley - Ho Ho Horsley
Kingston - Three Kingston
Liss - Lisstletoe
Malden Manor - Malden Manger
Martins Heron - Martins Herod
Mortlake - Merry Mortlake
New Malden - New Mald Wine
Pinhoe - Pin Ho Ho Ho
Poole - North Poole
Queenstown Road - Quicetown Road
Raynes Park - Raynesdeer Park
Salisbury - Salisberries
Shepperton - Shepherdston
Sholing - Sho Ho Ho Ling
Southampton Airport Parkway - Snowhampton Airport Parkway
Southampton Central - Snowhampton Central
Surbiton - Snowbiton
Sunnymeads - Snowymeads
Sway - Sway Bells Ring
Tisbury - Tinselbury
Tolworth - Misle Tolworth
Twickenham - Twinkleham
Upper Halliford - Upper Hollyford
Upwey - Unwrapwey
Vauxhall - Deck The Vauxhall
Waterloo - London Winterloo
Weymouth - Sleighmouth
Winchester - Winterchester
Winchfield - Grinchfield
Windsor & Eton Riverside - Windsor Wonderland
Woking - Wo Three Kings
Wraysbury - Wreathsbury
Back in December 2020 C2C renamed many stations for about a week leading up to Christmas on all of their CIS boards:
Chalkwell - Chalkwelf
East Tilbury - Elf Tinselbury
Laindon - Laindeer
Leigh On Sea - Sleigh On Sea
London Fenchurch Street - London Frostchurch Street
Shoeburyness - Snowburyness
Stanford Le Hope - Santaford Le Hope
Tilbury Town - Tinselbury Town
Rainham - Raindeer
Upminster - Upmincepiester
West Ham - West Glazed Ham
West Horndon - West Ho Ho Horndon
Back in October 2023 GTR renamed many stations for one day only for Halloween on all of their CIS boards:
Billingshurst - Chillingshurst
Brighton - Frighton
Crawley - Creepy Crawley
Huntingdon - Hauntingdon
Winchmore Hill - Witchmore Hill
Then there is Southeastern who rename London St Pancras International on their CIS boards on Pancake Day every year:
London St Pancras International - London St Pancake
Also at Southeastern again they rename London St Pancras International on their CIS boards on St Patricks Day every year:
London St Pancras International - London St Patricks
Not the same as renaming stations but there has also been cases of TOCs adding special messages to boards for various special event things.
I quite like these fun name changes but i do worry that they confuse unfamiliar passengers or foreigners with limited English language knowledge.