The campaign, created by Wieden & Kennedy London, comprises two TV spots with the first airing today (2 September).
The first spot shows a girl wearing a leather biking jacket from TK Maxx who decides to take up an unusual new hobby that fits her new outfit.
A second spot, airing in the UK on 8 September, will show an astronaut doing her make-up in space.
The ads were created by Mark Shanley and Paddy Treacy at Wieden & Kennedy London. The activity is supported by print, outdoor, digital, social, mobile and PR activity. TK Maxx's in-house team will manage in-store and digital creative. Mindshare handles media.
TK Maxx group brand and marketing director Deborah Dolce said the campaign played up the unpredictable nature of what consumers might find and end up buying at the shop.
She said: "This new campaign dramatises the real-life TK Maxx shopping experience with a brilliant twist of style and humour, which we hope will encourage new and existing fans to embrace the opportunity of big labels at small prices.
"Ridiculous possibilities might be that designer item you never thought you could afford, the chance to overhaul your wardrobe and home with quality items or the chance to try something new."