Is there anything preventing this from happening? Is it a possible scenario?

ns1.edgecastdns.net. 172,800 IN (Internet) A (IPV4 Host Address) 192.16.16.5

ns1.edgecastdns.net. 172,800 IN (Internet) AAAA (IPV6 Host Address) 2606:2800:3::5

These two records have the same name so I think it could be serving the wrong record.
['https://serverfault.com/questions/742224', 'https://serverfault.com', 'https://serverfault.com/users/326614/']
It's always possible that the DNS server could be buggy but it seems unlikely. If you query for a record of a particular type, that's the type you should get.

However, it is common for DNS servers to answer questions that haven't been asked as an optimization. In this case, it does appear to supply AAAA records as 'additional answers'. That's perfectly fine. 

```
QUESTIONS:
    ns1.edgecastdns.net, type = A, class = IN
ANSWERS:
->  ns1.edgecastdns.net
    internet address = 192.16.16.5
    ttl = 3582
...
ADDITIONAL RECORDS:
...
->  ns1.edgecastdns.net
    has AAAA address 2606:2800:3::5
    ttl = 63143

```
In a word: ***NO***

When you ask for an "A" record (IPv4), you will get an "A" answer or nothing. Likewise, when you ask for a "AAAA" record (IPv6), you will get a "AAAA" answer or nothing.

(IPv4 and IPv6 are *different* protocols. Just because they share the letters EYE and PEE, doesn't mean they are even remotely compatible.)

**Ask for an "A"**

```
~/[05:35 PM]:host -d -v -t a www.yahoo.com
Trying "www.yahoo.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50970
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 4, ADDITIONAL: 4

;; QUESTION SECTION:
;www.yahoo.com.                 IN      A

;; ANSWER SECTION:
www.yahoo.com.          240     IN      CNAME   fd-fp3.wg1.b.yahoo.com.
fd-fp3.wg1.b.yahoo.com. 30      IN      A       98.138.252.30
fd-fp3.wg1.b.yahoo.com. 30      IN      A       98.138.253.109

;; AUTHORITY SECTION:
wg1.b.yahoo.com.        55959   IN      NS      yf4.a1.b.yahoo.net.
wg1.b.yahoo.com.        55959   IN      NS      yf3.a1.b.yahoo.net.
wg1.b.yahoo.com.        55959   IN      NS      yf2.yahoo.com.
wg1.b.yahoo.com.        55959   IN      NS      yf1.yahoo.com.

;; ADDITIONAL SECTION:
yf1.yahoo.com.          56036   IN      A       68.142.254.15
yf2.yahoo.com.          56036   IN      A       68.180.130.15
yf3.a1.b.yahoo.net.     55420   IN      A       68.180.130.15
yf4.a1.b.yahoo.net.     55420   IN      A       68.180.130.15

```

You get an "A". (well, CNAME and it's "A"'s)

**Ask for a "AAAA"**

```
~/[05:35 PM]:host -d -v -t aaaa www.yahoo.com
Trying "www.yahoo.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7501
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.yahoo.com.                 IN      AAAA

;; ANSWER SECTION:
www.yahoo.com.          205     IN      CNAME   fd-fp3.wg1.b.yahoo.com.
fd-fp3.wg1.b.yahoo.com. 49      IN      AAAA    2001:4998:44:204::a7

```

You get a "AAAA".

**Ask for "any"**

```
~/[05:35 PM]:host -d -v -t any fd-fp3.wg1.b.yahoo.com
Trying "fd-fp3.wg1.b.yahoo.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17586
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;fd-fp3.wg1.b.yahoo.com.                IN      ANY

;; ANSWER SECTION:
fd-fp3.wg1.b.yahoo.com. 52      IN      A       98.138.253.109
fd-fp3.wg1.b.yahoo.com. 52      IN      A       98.138.252.30
fd-fp3.wg1.b.yahoo.com. 52      IN      AAAA    2001:4998:44:204::a7

```

(If I asked for www, I'd get only the lone CNAME.)

And if you want to see a "loaded answer"...

```
[root:pts/3{2}]debian1:~/[06:00 PM]:host -d -v -t any gmail.com 8.8.8.8
Trying "gmail.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55161
;; flags: qr rd ra; QUERY: 1, ANSWER: 16, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;gmail.com.                     IN      ANY

;; ANSWER SECTION:
gmail.com.              299     IN      A       64.233.185.19
gmail.com.              299     IN      A       64.233.185.18
gmail.com.              299     IN      A       64.233.185.83
gmail.com.              299     IN      A       64.233.185.17
gmail.com.              299     IN      AAAA    2607:f8b0:4002:c09::12
gmail.com.              3599    IN      MX      30 alt3.gmail-smtp-in.l.google.com.
gmail.com.              21599   IN      NS      ns4.google.com.
gmail.com.              21599   IN      SOA     ns1.google.com. dns-admin.google.com. 2015031901 21600 3600 1209600 300
gmail.com.              3599    IN      MX      10 alt1.gmail-smtp-in.l.google.com.
gmail.com.              3599    IN      MX      20 alt2.gmail-smtp-in.l.google.com.
gmail.com.              21599   IN      NS      ns3.google.com.
gmail.com.              3599    IN      MX      5 gmail-smtp-in.l.google.com.
gmail.com.              21599   IN      NS      ns2.google.com.
gmail.com.              3599    IN      MX      40 alt4.gmail-smtp-in.l.google.com.
gmail.com.              299     IN      TXT     "v=spf1 redirect=_spf.google.com"
gmail.com.              21599   IN      NS      ns1.google.com.

```