Hooper, who started playing for non-League Grays before being picked up by Southend, is 23 but was under 21 at the start of England's European Championship campaign.
He is the shock inclusion in a 31-man squad that includes Kieran Gibbs, Micah Richards, Jordan Henderson, Chris Smalling and Jack Rodwell for the matches against Denmark in Viborg on Thursday week and Iceland at Preston the following Monday.
On Fabio's radar? Gary Hooper had been linked with a senior call-up earlier this month
Andy Carroll and Jack Wilshere are two big names missing but they are now part of Fabio Capello's senior side, who face Wales and Ghana.
ENGLAND U21 SQUAD Fielding (Blackburn), Loach (Watford), Smithies (Huddersfield), McCarthy (Reading), Baker (Aston Villa), Bennett (Middlesbrough), Bertrand (Chelsea), Caulker (Tottenham), Gibbs (Arsenal), Mee (Man City), Naughton (Tottenham), Richards (Man City), Smalling (Man Utd), Tomkins (West Ham), Walker (Tottenham), Albrighton (Aston Villa), Cork (Chelsea), Cleverley (Man Utd), M Davies (Bolton), Henderson (Sunderland), Lansbury (Arsenal), McEachran (Chelsea), Muamba (Bolton), Rodwell (Everton), Rose (Tottenham), Sinclair (Swansea), Delfouneso (Aston Villa), Hooper (Celtic), Sturridge (Chelsea), Welbeck (Man Utd), Wickham (Ipswich).
Under 21s boss Pearce, who has possibly named such a big squad because there were so many withdrawals for last month's 1-0 defeat against Italy, has also selected Bolton's Mark Davies and Aston Villa's Nathan Baker for the first time.
Danny Welbeck returns after a recent spell on the sidelines with injury along with Kyle Walker, who was drafted into the senior squad for the 2-1 win in Denmark.
Pearce has challenged his players to impress ahead of this summer's European Championship in Denmark.
He said: 'There are one or two fresh faces in there such as Gary Hooper and Mark Davies but in the main the majority of the players are well known to us and have been involved in the qualifying for the tournament.
'Now's the time for all of the players to impress in the minds of the coaching staff that they want to be the ones stepping on to the plane. At the end of this meet-up I need to be able to make some final decisions about my squad and I will.
'Both of the teams we'll face will be in the Championships so there can be no better warm-up opportunity for us and there will be no underestimating anyone on our part. I expect the opposition will be thinking much the same about us.'
Matt Lawton: Capello can expect a backlash if the axe falls on FerdinandMARTIN SAMUEL: Behind closed doors John Terry has proved he is England's natural leaderCeltic and Aberdeen could face each other in cup semi-final for second timeReds skipper Gerrard out for a month and will miss England clash with Wales
Explore more:People: Fabio Capello, Andy Carroll, Jack Wilshere, Danny Welbeck, Stuart Pearce Places: Italy, Denmark, Ghana, Wales, United Kingdom