"I didn't even know when the game was and it came as a bit of a surprise," he says.
It's next Thursday, Glen.
"I will have a few friends watching and it will be nice to be back at Upton Park."
"I am not worried about the step up to the U20s and it will be the biggest crowd I have played in front of as far as Upton Park is concerned."
Glen, who is midway through a three month loan spell at the Den, says:
"Things are good at Millwall; we are tenth in the league now and hopefully we can beat Palace on Saturday."
Glen says there is not a huge transition to life in the first division, and adds:
"The only difference is that I get treated like a first team player, which I am obviously not at West Ham.
"Otherwise, it is similar."
Glen is keeping an eye on first team matters at West Ham and, talking about the Soiuthampton defeat, he says:
"West Ham dominated the game to be fair and I thought they were the better side.
"On another day, in another week, those chances go in and then we smash them about 4-0.
"But that is the way our luck is going at the minute, but I reckon it will change."
The squad for the U20 game is as follows:
Ambrose,Darren - Ipswich Town FC
Bent,Darren - Ipswich Town FC
Bowditch,Ben - Tottenham Hotspur FC
Carruthers,Chris - Northampton Town FC
Carter,Darren - Birmingham City FC
Cole,Carlton - Chelsea FC
Davenport,Calum - Coventry City FC
Dawson,Michael - Nottingham Forest FC
Garry,Ryan - Arsenal FC
Grant,Lee - Derby County FC
Hoyte,Justin - Arsenal FC
Johnson,Glen - Millwall FC
Lonergan,Andrew - Preston North End FC
Moore,Stefan - Aston Villa FC
Morgan,Lionel - Wimbledon FC
O'Neil,Gary - Portsmouth FC
Thomas,Jerome - Arsenal FC
Tonge,Michael - Sheffield United FC