Originally Posted by wakey:
“Seriously you are listing How I Met Your Mother as having an unknown cast when It stars Alison Haniggan (7 Seasons of Buffy, a number of episodes of Veronica Mars and the American Pie movies), Neil Patrick Harris (Star of Doogie Howser MD TV Show and major roles in the Harold and Kumar movies and in the first Starship Troopers movie. Also award winning stage performer). Even Jason Segel had stared in Judd Apatows two critically claimed TV shows (Freaks & Geeks and Undecelared)
And I can name many shows with casts who have a weaker uk reconignition than Parenthood when it was picked up by a UK network
Glee [from the creator of Nip/Tuck]
Mentalist [from the co-creator of Rome]
Rules of Engagment (arguably Patrick Wharbuton and David Spade)
Gossip Girl (Kristen Bell) [from the creator of The O.C.]
90210
The Mindy Project (quite a few of the cast are well known, but there's nobody stand out famous) - Too early to call success wise
The Office (Steve Carrel) - Not a UK success
Parks and Recreation - Not a UK success
Arrow (recurring guest star John Barrowman)
Beauty and The Beast - Not a UK success (barely a US success)
Supernatural (arguably Jeffrey Dean Morgan, but that's incredibly shaky)
Rookie Blue - Not particularly a UK success, but it was acquired as part of a multi-country deal
30 Rock (Alec Baldwin) - Not a UK success
Grimm [from the executive producer of Buffy]
And even the following probally have slightly weaker casts
Revenge
Once Upon a Time (Robert Carlyle) [from some of the writers behind Lost]
And that's just shows that are airing this season. You can go back and find plenty of shows UK networks have picked up with cast with less marketability in the UK”
I think none of the stars of HIMYM were instantly recognisable big name stars, though NPH was probably borderline (definitely is now). It also bounced around 3 different networks before finding a long lasting UK home.
Most of those weren't a success in the UK or had big name producers. Some of them even had big name cast members. I've updated your list with reasons they were probably acquired (or why they shouldn't count).
And my comments were more the fact it was a little known non-feel good comedy drama about a family with a disabled child, with moderately well known stars and an actor who is now famous for being blindly conservative, rather than his career, all combined to mean your lucky anyone picked it up.