Terence is my two year old son's favorite train from the the Thomas books. We bought him the wooden Terence from a local toy store, only to discover that his treads came off about thirty seconds after he came out of the box. This was a real pain - I put the treads away and let my son use Terence like a regular train, which he didn't mind too much but it was a bit upsetting to pay ten dollars for a toy and then have it be poor in quality.
A few days later, we were at a different toy store and saw that Terence had been redesigned! Unfortunately, the store we had bought him from doesn't do refunds, only exchanges. I went home and called Learning Curve's 800 number, and a very nice customer service lady gave me an address and told me that they would replace my son's Terence with the new one.
I mailed him back, got the new one in a few weeks, and he's GREAT. The treads don't come off, he rolls on plain table, track, and even the carpet wonderfully. My son was very happy as he had wondered what happened to his old Terence.
Learning Curve has a lifetime garuntee on all their products so if you have the old Terence I reccommend giving them a call and they will let you exchange it for a new one (even if you bought it three years ago!).